Modern engine control musings and Fixing a Figaro
Вставка
- Опубліковано 14 жов 2024
- Yep. It's pretty much just that. Links to the Aging Wheels videos about this weird little car are down below;
Review:
• The Nissan Figaro is a...
Repairs:
• Let's Fix What's Wrong...
Me driving the finest in East German engineering:
• Technology Connections...
Mechanic here. The MAF looked clean at the beginning of the video. When that type gets dirty, it's very noticeable dark dirt covering the sensor wires. When clean they appear white-ish and somewhat translucent. That type of MAF, btw, very rarely goes bad, but often gets dirty. Probably the reason it starts easily in the cold, is that it (most likely) has a cold start injector, which will be used in the cold to shoot a lot more gas into the engine to get it to start. So, really, you're probably looking at a lean condition. Suspect vacuum leaks. Oxygen sensor will not cause a poor start, as the computer will ignore it entirely for a minute or so until it's sure that the sensor is warmed up. This time will be less if the sensor has a heater (more than one wire), but still starting will not be affected by it.
If you have a cam/crank correlation code, fix that. Likely the distributor is not adjusted correctly, hopefully there is an adjustment. I'm not sure of the procedure. It's likely you will need to find a real mechanic who has an old scanner than can talk to pre-OBDII Nissans. I do, it's not terribly uncommon. This car should have a scanner plug. Perhaps behind that panel with the button and LEDs.
Also, rockauto.com dude. They don't list a Figaro (big surprise) but you only need to divine which model is comparable. Sadly, I can't see that valve available there. Perhaps if you had a part number.
Speaking of valves, remove the IAC valve and clean it thoroughly. This one should rely directly on coolant flow and temperature. The coolant passage through it can get gummed up and seize the moving part.
Also, the intake air temperature sensor might also cause this problem.
If you’re going down the stuck valve route, check/clean the EGR (if this car has one) - for vacuum leaks, IAC, EGR and the throttle itself are all suspect because they’re all connected to the manifold. Further, when looking at/cleaning the throttle, check the throttle position sensor: that’s where the computer looks first (in conjunction with MAF) for injector pulse duration. Then there’s fuel pressure regulator, and EVAP valves to take into consideration. And the gas cap if the EVAP system is in question. As in contracts/law, it’s the little details that cause the big headaches.
Yar Nunya I don’t recall you mentioning it. It’s the type of maintenance that’s overlooked until problems occur. Proactive prevention rather than reactive repair is my mindset.
Also, this car obviously has the door-style MAF, since that's the housing you see on the air cleaner assembly. Not a hot wire type. The door style was very common on early-90s Japanese cars.
@@immikeurnot I mean, he literally takes the sensor out and shows us in the video. It's a hot wire type, like an old GM or Ford.
immikeurnot I don’t give thumbs down unless they’re deserved; yours was because of this: a vane type MAF is not what this car has, if you watched around the 3:00 mark of this video.
At 8:11, to the right of the mounting point for the MAF, I can see what may be a split vacuum line. Might explain your drivability issues. I have some experience with Nissan cars if this era, and it always seems to be a vacuum leak... loving your work, sir! Cheers and good luck! Edit: never mind, I see it is cracked insulation on the A/C line... my comment still stands, though. It’s always vacuum ☹️
I should definitely go around looking for vacuum leaks. So far, though, now that the MAF is clean the only issue is the (possibly) high idle and the extremely mild surging. Without knowing how the computer might do a re-learn that might just go away over time, or else it could be entirely unrelated. Pre-OBDII is fun!
that is a ac line it just a cover
still check for vacuum leaks. there is a few hundred miles of vac line on these things, and after this number of years, im sure there are a few leaks.
Might explain the high idle for sure. I would take a spray bottle filled with water to the vacuum hoses-- makes it easier to hear. If it doesn't seem to be a hose, I would check the intake manifold.
Start pilot or brake cleaner spray is an easy way to look for vacuum leaks. I'd also take the IAC valve out and clean it thoroughly.
"so this is a 1991"
Me: not too bad
"So that's nearly 30 years old"
Me: damn, I'm old!
Blair Churchill it hurt when I heard him say that.
Yeah, I can handle saying I'm 47 but when somedays "high school class of 1991 30 year reunion next year", that's when I feel old.
Scary, isn't it.
@@jeremymurphy7320 Having also graduated in '91 (but only being 46), I guess the good news is my class has never done a reunion.
I'm a '92! I'm almost as old as this car, which is almost 30! AAAAAAAAAAAAAAAAAAAAAAA
I absolutely love this and these kinds of videos from you!
Me too, me hissy,
🐍🐍🐍🐍🐍In a good way 🐍🐍🐍🐍👌👌🙂and also I have tesla coil and I play high voltage and light bulb and voila let there be plasma bulb 💡💡💡💡💡⚡⚡⚡👀🐍🐍🐍🐍🐍
@@Purple431 ⁹⁹⁹⁰⁰⁰⁰⁹⁹⁰⁰⁰00⁰0⁰⁰⁰⁰⁰09⁹⁹⁹
Same here :-)
2 + 2 = 5 for extremely large values of 2.
Yeah, but "2" isn't the same as "2.6" unless you're using extremely rough estimates with such small numbers. That's like saying "200,000" is the same as "275,000". The whole 2+2=5 political thing is dumb and has no place in modern mathematics, or,even in modern philosophy. It's a fallacy.
@@tyrantstomper it’s a calculus joke! Relax homie
@@spaceman884 calculus ugh. I've lately come to think that physics will be most accurately portrayed by n term newtonians or something in the future and continuous math would be the calculable approximation. For some reason I'm leery of adding infinite numbers of zeroes to come up with a number.
As it approaches the limit, of course.
Or extremely small values of 5.
How can a car from the 90s be 30 years old when the 80s were only 20 years ago?
You aren't being serious I hope.
1990 was 30 years ago.
spaz 1 15 thats the joke
I picked up on it after I made my comment.
Guess I should've read more comments first.
Mister McFly, I'm afraid you and your DeLorean have been SPEEDING and I'm gonna have to write you a ticket.
The perception of time is weird !
Good sir you and your Japanese Figaro have unknowingly solved an ever-ancient car problem I've been having on my own *American* vehicle and I thank you greatly !!
Also this is a pretty neat and incredibly informational car video from a tech guy. Most car guys' vids do such a terrible job at explaining stuff like this, seeing a tech channel explain this so eloquently. Nice!Good luck on the remaining repairs and happy trails! Thanks a ton!
They're the last thing everyone thinks of. I didn't even know they were a thing until mine failed.
As odd as this will sound, electronic fuel injection (EFI), as most viewers would understand it, has been around since 1957 but the first production system going into a car was 1958 with a Bendix system used in the DeSoto Adventurer, Chrysler 300D, Dodge D500, and Plymouth Fury. It wasn't great and only about 35 of them were ever produced over the four lines. The next major attempt of that Bendix system was in 1968 after it was sold to Bosch and used on the Volkswagen Type 3 E-models that was renamed to Bosch Jetronic then renamed again to D-Jetronic.
This system would be what many would consider a "modern" EFI as it has a common fuel rail that feeds individual injectors and a way to measure air intake. Many assume that electronic Throttle Body Injection (like you would see in early GM pickups and some of their V8 cars in the 90s and known as TBI and Single Point Injection or SPI along with a multitude of trade names) is older, but it isn't. The mechanical version is as it was used on aircraft in the 1940s but the electronic form was much later. TBI feeds a single or dual injectors that sit on top of the throttle body and looks kind of like a two-barrel carburetor that's missing its floats and jetting. It was so close that many ancillary carburetor parts work (like the air cleaner, fuel pump, lines, and even some intake manifolds) and is why it was cheaper for manufacturers to use. TBI is also thought to be archaic but is actually more modern as it was introduced around the 1980s (just like a pushrod engine is also considered "archaic" but is actually a newer engine design than overhead cam).
For throttle control, electronic "fly-by-wire" was introduced in 1988 with the BMW 7-series. The next big innovation of "modern" EFI was going from batch fire injection (either engine bank to engine bank in V-blocks to firing all injectors at once or two-cylinders at once in inline blocks) to multiport injection where each cylinder gets a squirt of fuel as needed. That happened around the 1990s, possibly even the very late 1980s.
Most engines have gone from port injection to direct injection (where the fuel injector sits inside the cylinder like a spark plug instead of the intake port) while some use a dual system where it's both port and direct injected. The big advantage of direct injection is that nearly any grade of gasoline can be used on an engine with only a minor degradation in performance. This is because the fuel is injected when the cylinder is nearly at its hottest and you're burning more air than fuel, much like a diesel and is where the technology kind of comes from. While we think of that as a 21st century invention for gasoline, it was first mass produced by Mitsubishi in 1996 with their 4G93 inline four-cylinder engine.
What we're starting to see today (at least from Maserati, but others are developing) is "pre-combustion," in which the spark plug is used only at low RPM/low engine load then at high load/high RPM, pre-ignited fuel enters the combustion chamber and ignites the air-fuel mix in the cylinder instead. Eventually, the idea is to get rid of the spark plug all together while still being able to use gasoline or an ethanol blend. The biggest stumbling block for anything like this is heat. As cylinder heat increases, so does nitrogen oxide (NOx and, no, not nitrous) production.
That's why most modern vehicles use an Exhaust Gas Recirculation (EGR) system as the spent gasses cool the cylinder by replacing the oxygen rich air, thus cooling the cylinder since there isn't any more air to use in the combustion process. Also, no, there isn't unburnt fuel when it is used in the cylinder and why the EGR exists. The main reason you smell more fuel is because the ECU is trying to compensate for the increase in temperature from more oxygen present in the engine as it monitors oxygen sensor data along with coolant temperature, ambient air temperature, and mass air flow data.
Geez, sorry for the article, but this is my forte as my channel name hopefully implies.
Well your close the the year. 1954 Mercedes-Benz came out with fuel injection. 1955 Mercedes-Benz 300sl was the first year for fuel injection. Where is the 57 Chevrolet on the list of production injected engines?
@@ducewagsThe 1957 chevy had MECHANICAL fuel injection, not efi. And there are different types of mechnical fuel injection too. The simple Hilborn/Kinsler used in dragracing and sprint cars. And the much more streetable and more complex mechanical injection of the 1957 chevy. And even the mechanical systems used in diesel engines...the P pump used in Cummins 6BT engines.
The Bendix systems in airplanes stinks...look at the hot start procedure for your favorite high performance general aviation airplane. Basically, the fuel instantly vapor locks when you shut down, and there's no compensation built into the 100% mechanical control mechanism. It's a lot of things like turning on fuel pumps, listening for ticks, and motoring the engine with the starter while moving the mixture control. Oh, and one of the possible consequences of screwing up is catching the engine on fire 🤣
Wow. I have learned a lot from you. Thanks.
@@darrenmorris869 and duce wags: The Mercedes cars were mechanical injection, as well
Your MAF was already pretty clean. Believe me, you'll know when it's dirty! It will have a blackish/brown dusty looking buildup. Also, they're not really all that fragile, you can use carb and choke spray or brake cleaner with no worries. Even the ones that have a warning telling you this sensor is coated and never needs to be cleaned. B.S! They all need to be cleaned in time and the coating don't mean a damn thing in terms of performance!
Somebody cares enough and knows what they're doing, that's why the O-ring was lubed!
All these older 4 bangers had the CPS (camshaft position) sensor in the distributor since the distributor is directly driven from the cam shaft. It's a 2 for 1 deal and quite logical really.
True true, we've had some sort of EMS (engine management system) since about 1975 and it was fully implemented across all manufacturers since about 1980. The electronic carburetor, boy oh boy, those were the day's of absolute hell on earth!
Okay, now that I finally heard the thing run, I can help:
0 --Open radiator, look under cap for coffee/chocolate milk build up.
1 --Check the ignition timing and adjust if out of spec.
2 --Clean the throttle body and throttle butterfly/plate with carb and choke cleaner and a tooth brush. Open the throttle and clean both sides of the butterfly, yes it matters!
3 --Check the the TPS (throttle position sensor) and adjust if out of spec.
4 --Measure IAT (intake air temp) sensor and simulate if out of spec using a POT (potentiometer).
5 --Measure ECT (eletronic coolant temperature) sensor and replace if out of spec.
6 --Check fuel pressure, replace fuel filter, regulator or pump if out of spec.
7 --Lastly, measure (key on engine off) MAF reading. If out of spec, replace sensor.
By your description of symptoms, I don't think you fixed it, everything runs better when it's warm! We can get into cleaning grounds and compression/leakdown tests, but the list above will give you an answer as to which direction to head moving forward. And to, you can check it all in about 30 min. In another life, I used to get paid $45.00 per hour for this information. You are welcome 😜
So much this. And this would done in half the time, if that ecu had any sort of computer diagnostics.
Those old Mitsubishi trucks with the electronic/vacuum controlled carbs are the worst 😂😂😂!!!
@@hojnikb :
This is back in the day when a paper clip was required to flash a CEL (check engine light) code. OBD version 1.
Back when, it all had to be measured on a resistance or voltage scale. It's really dirt simple how these engines were run, but the ECU (electronic control unit) would typically show 'at best guess' what it thought the problem is or was.... In this era, we manually test and prove it all. Honestly, I kinda miss those days!
Now every kid on the block can read a code and replace a sensor, but never understand what the sensor is let alone what the sensor actually does. Just because OBD (on board diagnostics) has improved, does not mean it's without fault. If you didn't learn it the hard way before, now with modern tech you probably never will. But please remember, a code does not mean anything until it's repeatable and finally 'proven'. You have to manually test and keep on testing until you can reach that conclusion!
If you want to experience a real life butt hole pucker situation:
Diagnose an $800.00 PCM (power-train control module) and tell your customer he/she needs a new one..... Be ready to prove it!
@@mlyssy2:
Don't forget about the Honda ECCCCCSsss's. Vacuum line torture and solenoid nightmares! And that's before we start talking about wax pills and ECM control 🤣!
Finite Tuning omg! All of those ‘80s Japanese solutions at skirting true fuel injection were horrible nightmares! I’m not sure if they were just reluctant to actually go with at least a tbi or if they were holding back for the next generation but how dumb was it? I mean, GM was putting tuned port and multi port into everything they had so why would the leaders in tech just keep dumping money into ancient technology? It’s beyond me.
I would be looking for a vacuum leak. Vacuum leaks are especially problematic on MAF equipped engines. Any air leaking in is “Unmetered” air that the ECM doesn’t know how to account for because it bypasses the MAF’s ability to read that air intake. Surging can result in that instance because the engine senses the RPMs going up (because of the air leaking in uncontrolled) and it tries to bring the RPMs down with that Idle Control. Then it senses it overcompensated and goes back up. Repeat and Repeat.
The Code 11 is a bit concerning. Where did the new Timing Belt come from? I’ve had issues with Nissans and Aftermarket timing belts in the past. The Marks line up but sometimes the length of the belt is JUST different enough that the engine ends up being 1 or so teeth out of cam timing, despite the marks matching up. The last time that happened I had to get a Nissan belt and it fixed my issue right away.
The timing belt came from The Figaro Shop in the UK so I'm certain it's a fine part.
Also - I much prefer the term "pirate air" :)
@@TechnologyConnextras well "Pirate Air" will plunder your fuel and burn your catalytic converter to the water line when it's done with you!
.... Yea ok, that's better.
Find an older mechanic/ one that specializes in older Japanese cars, that still has a "brick". It's an older Fap-On scantool, that allows one to actually monitor the area(s) of potential concern.
@@16v15 considering the age of the car and the fact it's japanese, it's highly likely there's no diagnostic port period, as they weren't required there at the time. the LED's may be all you get.
@@cpufreak101 Most Nissans made from 1990 to 1999 have a Consult port. It doesn't seem the Figaro does, but most did, even Japanese market ones.
The cam sensor being in the distributor is pretty standard. The cam is what runs the distributor.
I have to keep an extra distributor in the trunk of my Saab this reason. good thing it only takes a few minutes to swap out on the side of the road...
They're usually some form of hall effect sensor though in my experience, not a "cam" sensor. Still a sensor to detect timing, so it's the same difference lol
Hot wire sensors generally have the two wires connected as two legs of a Wheatstone bridge with fixed resistors making up the other two legs. Sufficient current is passed through the wires to heat them and the wire used changes resistance with temperature. One wire is placed in the air flow, the other in stagnant air. The wire in the air flow is cooled by the moving air, the stagnant wire is used to balance out the ambient temperature. The amount of heat removed is proportional to the mass of air impacting the wire, so the bridge voltage is fairly linear with mass air flow.
Sorry for the rambling description, but I think you will get the idea. I used to use christmas tree bulbs for flow sensors that way. Carefully break the glass with pliers to expose the filament and you can detect very low air flow rates with it.
Congratulations. You and the Mythbusters: the only people I've ever heard talking about stoichiometry. I imagine there's some sort of prize for that.
@@TemperatureHot He mentions the word a lot when talking about engines
Yes, 14.7:1 ftw. The best ratio.
Hearing that word gives me nightmares
Having worked on a bunch of other finicky cars from this era, I'd suggest the two most likely causes are a failing "intake air bypass valve" or a source of unmetered air. The intake bypass valves are known by many different names depending on the make of the car(bypass control valve, air intake control calve, etc). These computer controlled valves generally allow air to bypass the throttle plate or body and can be plumbed into exhaust or coolant to adjust by engine temperature. This gives engine ECU the ability to control the air/fuel ratio when the throttle is closed during cold/hot start conditions(functioning similar to an electric choke)as well as fine engine speed control. A sticking or slow bypass valve or a leak in any vacuum line or leaks/holes anywhere in the intake system after the MAF(this includes intercooler, piping, etc if equipped) can cause this condition.
As the owner of multiple 91-95 North American manufactured vehicles, I second this. Idle air control valves are a common rough idle issue, as are exhaust gas re-circulation systems. Thankfully by the early 90s most air injection pumps (common in the 70s/80s) were a thing of the past. Hard to believe, but vacuum plumbing is one aspect of modern cars that has gotten much simpler in the last 40 years.
Exactly, poor idle and surging under partial throttle sound like a textbook vacuum leak. The IACV is probably bad, or there's a hose somewhere that needs to be replaced.
I really like the un-scripted format of this video. (Don't know about the other vids, as this is the first one I've seen).
Your idea of using a scanner to show us wat (and how) car computers work, is an excellent one. I have personally built and raced an engine @ Bonneville (a 620hp 502 Chevy in a 1932 Ford, 176 mph) it was completely mechanical in nature, and I understand the basics of computer controls, but I ALWAYS learn something from you, even if it's familiar subject matter.
For starters, I love this video from you. Totally unscripted and off the cuff. 2nd, the start-ability issue might be a seal issue in the fuel system, where the fuel is leaking out of the fuel line going to the engine and it takes a bit for the pump to re-pressurize the line before the car will actually start. I am impressed on your knowledge of the actual workings of the sensors of the car and how they all interact. I was not expecting that. I look forward to additional videos like this.
the
car
is
ADORABLY CUTE
These heated wire air sensors are quite neat. Very accurate, yet so simple.
Used to work in HVAC and we used tools like these for adjusting ventilation. You type in the pipes dimensions and you got a reliable litre per second value. For bigger rectangular pipes you took several measure points for a calculated average. Taking turbulence into account.
Really like these non-traditional videos and the crossover series.
When you find a more modern car to plug into, it might also be neat to get a device that also allows programming directly back via the same scanner port - for example the Carly product works with VW group and BMW and you can change basically all the things, from door chimes to performace stuff and more via their app. Also this is not an advertisement for that product, but I do own one.
My favorite part of listening to Alec talk is that it makes me realize that it's exactly how I talk about things that I'm capable of understanding but I don't (yet) fully understand.
You’re car is just like you. Neat, a conversation starter, and slightly problematic...
"You are car is just like you"? ...ok
This reminds me so much of chasing problems in my first car. It was a Mazda but similar enough to yours. There's a lot of comments saying to look for vacuum leaks which is good advice but none mention how incredibly tedious that can be. In my Mazda there was an undetectable leak that led me to replace basically every hose, gasket, and clamp along the intake system which solved it for a few hundred miles before the gremlins got to it again with electrical issues, which are even more annoying! I'm grateful to live out of the suburbs and not need a car anymore lol. Shout-out to my city's transit system.
The MAF has 2 parts to it: The thermometer and the hot wire. The thermometer is, well, a thermometer. It measures the incoming air temperature. Using *that*, it heats the hot wire to 100C over the air temperature. The more power it takes to maintain the heat on the hot wire, the more air is flowing through.
I'm semi-confident this is correct.
This is pretty much correct, one of those wires is held at a fixed temperature above the other and the power required to do so is proportional to airflow. The actual temperature difference may not be 100C for every MAF however.
I'm certainly excited for those upcoming videos about the sensors. I work at an auto parts store, and it'd help me so much explaining how things work to people with the visual aid of an oscilloscope
Part of your issue could be coming from the split in one of your vacuum hoses as well as the mass air flow if the split is on your idle control side then your o2 sensor will see more air than it should and that will lead to engine surge
MAF sensors are a devious little beast. They can be catastrophic when they fail, and the symptoms are confoundingly close to those of many more common engine failure causes. They are the last thing people think of when trying to work out why their car is not starting. Been there, done that, bought the tshirt!
Hi Alex, the idle speed should be around 1000 rpm at idle, you can adjust it with a plain screwdriver in the most front hole of the ones on the right side of the ECCS. You can find service info like that from GJ Northall in UK on the internet.
If it wont start in park, try pushing the stick more forward, while you turn the key. There is a 29 year old plastic sensor somewhere downthere, which might need a little persuasion.
I found your channel via the Aging Wheels Figaro Video. I have a Pale Aqua Figaro here in Denmark, which I made one YT video with recently. Your channel is really good, and I just bought a Kindle after seeing your E-Ink video! 😎
- How did you get oil on top of the turbo shield? That is going to smell, when it gets hot 😉
The ECU adjusts the idle solenoid duty cycle and ignition timing trim to reach the target rpm. Only the base idle needs to be adjusted.
Warm the engine up first to operating temperature(Below 80c most ECUs fuel, idle and ignition timing will be in warm up compensation). Turn the engine off, disconnect the Throttle Position Sensor(TPS) and (AAC Valve)idle solenoid connectors. Start the engine, at this point the ECU is in maintenance mode, for base idle and ignition timing adjustment. When done, turn off the engine replug the connectors.
Not doing this, can cause poor idle, loss of power or engine damage due wrong Ignition Timing. This has worked for my '87 Sentra all the way to my R34 Skyline.
Idle screw shouldn't be messed with. If it doesn't idle, you're just masking the problem and introducing new variables
The high idle and surging reminds me of the 1994 Mazda 626 that I drove in high school. It had partially sucked its intake manifold gasket in and had a horrible vacuum leak. It also had a similar type of diagnostic code system, so this video brings back so many memories. I miss that car...
14:22 that warning label actually looks like a sticker saying the timing belt was changed at the written in mileage and date.
and also to please change it every 100,000 km
@@thoperSought aging wheels just replaced the belts so no problem
Those are probably my favourite dashboard dials of any car I've ever seen.
I think the wording for your camera setup to focus properly is :"Focus you FAK"
Source : AvE
Why can't I ever have an original thought...
@@frykasj yeah, me neither, I even yelled it!
I either go AVE or big clive when things don't focus
I yelled it at the screen... seemed wrong to not have SOMEONE say it.
Source checks out.
Vintage automobile dashboards are such a feast for the eyes. Nice little beauty you have there.
You have a massive factual error at the start of your video. A nearly 30 year old car is from the 1950s. I will be taking no questions at this time.
I see the joke in here. A car from the 1950s is technically around 70 years old.
Those are exactly the cars they don't make anymore. I remember hearing this comment all the time in the mid 80s.
@@piratetv1 I remember seeing this comment on UA-cam all the time in the mid 80s.
@@davemarm i didn't know what a youtube was going to be in the mid 80s, i just grew up with car people who didn't like the idea of uni-bodies, plastic bumpers, and needing special tools to get into small places. They'd say things like "i remember when you could fix anything on your car, yourself".
@@piratetv1 and you had to, because the cars were always fucking broken
There's likely a vacuum throttle solenoid to control idle. They've been around for a long time. My 79 Ford had one that'd set the cold idle higher while the choke was on.
Here I’ve just been staring at that thing to the rear of the valve cover wondering if it’s supposed to say EGGS
Used to be an Engine Performance / Engine Controls engineer until I was made redundant this year and now work on comparatively dull things. Just two and a half minutes in but it's making me smile to see someone get interested in engine controls :)
Can you legally drive that in America?
If it's more than 25 years old it's legal and most old mail trucks in America is RHD
Yep! Anything over 25 years old is exempt from following US regulations.
Yep, just wait until 2024 when the US will single-handedly take every single Nissan Skyline R34 GTR from Japan
@@phazonlord0098 I've been saving my pennies! So far I have...$5.12 saved up. In pennies. Think that'll be enough?
@@tarstarkusz Any insurance company that's willing to ensure a classic car would probably insure it.
Figaro owner in Michigan here. I had the park safety switch issue and it’s a common issue but easy to fix. There is a cable connecting the shifter to the transmission. There are plastic bushings on each end where the ends attach. On mine these were brittle and cracked and one was even missing half... without these bushings the shifter simply isn’t moving the cable far enough to engage the switch.
Anyway, these are just a few bucks apiece and easy to install, especially if you have a hoist. 15 minutes and I had both of mine replaced.
The thumbnail made me think this was a Mustie1 video...
My first 4 cars were 80's-early 90's Japanese. Every single one of them had odd electrical quirks and features. It's amazing how much tech engineers were able to cram into these cars, but it is also the most failure prone point.
On the other end of the spectrum, I have two 100% mechanical diesel engines (same model), one in a 1987 Ford pickup and the other in a 1985 Ford E350 chassis motorhome. The only thing electric that the engines need once the motor is running is a fuel shut of solenoid. With no 12V going to it, the fuel is cut off and the motor stalls. That is how these motors are shut off actually. It's hard to find someone who has the equipment and experience to time the motors.
yeah, you can literally convert the 12V solenoid to mechanical and "live without electricity" (maybe except starting the engine)... i've seen the diesel timing procedure, it's based on the micrometric position of a plunger in the center of the fuel injection pump, there are micrometers intended for this
@@redoverdrivetheunstoppable4637 i don't know how it works on mine exactly but you have to rotate the pump slightly in one direction or the other depending if you want to advance or retard timing. People use a wrench and turnbuckle to do it.
@@cubey that's what you do to adjust it but you need to know if you hitted the perfect timing and you need a micrometer screwed on the pump to see what you're doing, if i remember correctly the plunger must move 1 millimeter from the bottom when the engine is at top dead center... there's a small screwed cap on the pump in the middle between the outlet tubings, that's where you screw the micrometer ... never done that but i've seen it, i worked as a mechanic
The auxiliary air valve you mention is adjustable - loosen the locknut and set the hole in the disc to give a higher cold idle which is probably all the engine needs.
Try searching for a vacuum leak i’ve had it before where the leak has caused hunting due to bypassing the mouth sensor Which will make the ECU think the engine is running lean and try and correct it which will make it to hunt. I had the exact same problem on a different car I spent a good morning trying to figure it out and it turned out to be a perished line on the master brake cylinder which I would’ve never expected
I had a similar problem which turned out to be a missing vacuum line cap on the vapor recovery canister.
As mentioned by a bunch of other comments...check for vacuum leaks, check coolant for air pockets, check for boost leaks between turbo compressor and intake manifold. These older cars use coolant flowing through idle air control valves or even a seperate solenoid that temporarily raises idle at cold start like a choke on carb.
Nissan's are notorious for Idle Air Control valves and if egr is equipped dirty EGRs causing issues too.
"controlled all electronically"
I see those vacuum tubes you cant fool me
I’ve got an ‘88 Mazda, and while it has vacuum lines, the only things directly actuated by vacuum are the brake booster and turbocharger bypass valve. The vacuum signal to things like the EGR and charcoal canister are switched by solenoids
6:30 - Auxiliary air valve, little bimetal strip heated by electricity to close a rotary port as engine heats up. Some/many engines had water lines going to it as well so it doesn't reopen while the engine is off for a few minutes while warm. These are a hallmark of a Bosch derived system - as are the rectangular plugs on all your injectors and other components.
Yes, commonly used on Bosch K-Jetronic systems. Even perfectly functioning it relies on engine vibrations to move. I can imagine that it fails to open as the engine is cooling down. If so, a little tappy-tap-tap before cold start should help.
"Mass Air Flow Sensor" tickles all of my chemical engineering senses. Now just get me a process diagram and some equations to solve, and I'll be at home.
Best I can do on short notice: ocw.mit.edu/courses/mechanical-engineering/2-61-internal-combustion-engines-spring-2017/
:-D
My early 90s Mini is 100% mechanical. It’s pretty fantastic when something goes wrong. Watching this reinforces my fears of owning an older car with an ECU.
It probably just wants to live in britain, where "room temperature" cold-starts aren't a thing... :P
That is a very neat little car! I really like those gauges, very basic but still stylish. And of course, the "dummy lights"...I like the way they are all lined up. Hope you get it figured out!
That hose next to the mass airflow sensor looks sad.
I love that you delve into new fields whether or not you're comfortable with the information you know in only the search of knowledge as a mechanic we call that behavior Idle hunting it's most likely because between the maf the air filter in the inlet itself all rubber and gaskets need to be replaced Maf likely an inlet leak
I just keep looking at the oil stain and want to wipe it lol
Intake air leaks are definitely worth a look. Smoke testing is the best method I've found for flushing out difficult to find leaks. As for the idle hunting air leaks could cause this but oftentimes on this era of Nissans the idle air controller or AAC as Nissan call it is carboned up, cleaning it with carby cleaner dramatically improves idle quality and clears up the hunting.
1:20 Correct, electronically timed, the distributor just directs the spark
1:55 vacuum leaks, if you can replace every vacuum/intake hose, do it.
6:00 at least on a pre 00 BMW, if you unplug the MAF and it runs better, problem is intake air measurement problem
7:20 good idea replacing temp sensor
7:40 vac leaks, or maf sensor.. vac leaks are cheaper :D
8:50 o2 sensors are a good idea, suer sensitive and easy to break, start WD40 spraying your old one now, just in case...
10:50 or when someone just bridges with wires together...
13:10 it'll for sure have a crank sensor, the error code you mention would be that the two signals were not 'in time'
14:25 I have E34 M5, such a pleasurable guilt.
15:25 for sure
"6:00 at least on a pre 00 BMW, if you unplug the MAF and it runs better, problem is intake air measurement problem
"
Pretty much every maf equipped car should run with maf sensor unplugged. In just goes to speed density mode and uses map and air temp (along with tps) to calculate the correct mixture.
My E34 pulled it's last dick move on me while i was selling it. Just as we were doing the paperwork, the MAF gave up. Buyer pulls out the plug and it runs fine again. Could had lasted 10 more minutes so i would had gotten a bit more from the car :D
This is a great example of why I prefer 70s and 80s cars; modern enough to be fairly reliable but simple enough I can do pretty much all repairs and maintenance myself.
I'll never stop regretting selling my hotted up 1981 BMW 633csi, fantastic handling, smooth and strong engine, 5 speed manual, and just about the simplest fuel injection system I've ever seen.
Edited to say: I love that little Figaro, it's freaking adorable!
More Connextras, yay!
I have a 1985 Nissan Skyline DR30 which is a 16 valve twin cam fuel injected engine and was the first production car fully sequentially fuel injected engine apparently. Anyway, it has a VAF or flappy volume air flow sensor. It also has an optical sensor in the distributor looking through a steel disc with many tiny holes. It was amazing how they did things back then. Good luck with the fig!
Has anyone called you a Renaissance man? I think anyone who can speak in detail, intelligently, about both cars and CEDs qualifies.
I’m old enough that I can legitimately say I remember an all mechanical car. I had a 74’ F-100. Best truck ever.
Load the parts cannon!!
Check out south main auto for some diagnostic tips
The distributor I had on a Mitsubishi (about the same age, more or less the same tech), looked like it was a straight bolt into the cams.
But when you took it apart, there was no solid connection. One side was a sensor for the cam, the other a motor.
It did alter the timing by rotation to suit, though as far as I am aware, it was more crude than the ignition packs we have now.
And basically knocked the whole sequence forward, or backward a few degrees relative to throttle position.
The throttle also had a direct wire, but again was split into a sensor, and motor. So the throttle was electric too.
11:51 Why would you need a sensor to tell where the engine is? It's in the car, alright.
Agree. If the engine is anywhere else, you don’t need a sensor to tell you that.
he meant cam/crankshaft position
Ladies and gentlemen, we have a comedian over here!
This is the exact car that I've wanted for several years now. it's fun seeing it here
I may have missed it at the start, but the high idle/rough start sounds a lot like what I had in my integra.
Bonus points for also having a cpk in the distributor
"They dont make cars like they used to" is technically true. Cars today are infinitely better than older cars. More power, better fuel economy, more features, and generally more reliable. It is fairly common to see a car from the 90s and of course newer. Once you go back to the 80s, the number of cars you will see drop drastically. Every decade you go back, you will see less and less. Sure you will see old cars that were babied, but those are the exception, not the norm. Why dont you see those cars anymore? Because they all broke down and were scrapped.
and modern cars are exponentially safer!
Well i drive a 85 ford f250 all mechanical never gives trouble just rounding up to 1.5 million miles and only thing ive done is oil changes and grease were it needs
And well tires and brakes
The only thing old cars have that new cars don't have is the cool factor and usually they're a lot cheaper.
You can see 80s cars rarely today, but you won't ever see a 2020 car on the street in 2060. A well made car is extremely reliable for the first few years of its life no matter if it was made in the 80s or today. What comes after that is the interesting part. When something goes wrong on a classic car it's super easy and cheap to fix because the part is simple so it's cheap, and the labour is free because, again, it's simple and you can do it yourself with an internet tutorial and no prior experience. The things that go bad are usually the rubber parts like bushings and hoses. The rest is just metal so crude there's just no way it can wear from normal use even in decades. Plus, more subjectively, the ride quality and comfort is just so much better in old expensive cars versus new ones. Why do they want to make every sedan sporty nowadays? Why are the suspension and seats so hard? There's nothing that I've tried today that compares to the comfort of an old mercedes or any (even older but sadly not as reliable today) american land barge for that matter.
I get your point. If I didn't want to work on my car or think about my car when I'm not in it, I would 100% buy something modern and trade it in for a new one in 5-10 years. But if you're a person who likes working on mechanical stuff yourself, there's nothing better than a quality old car, both in terms of comfort and long-term cost. They're also safer because you drive VERY carefully and VERY defensively in a car with no airbags :D
When you said "once it clears it's throat it's fine" made me think of a leaky injector (if this car them - could be TBI). I have run into injectors that leak down when the engine cools down and floods the intake with fuel. It cause's hard starting and poor idle until it "clears it's throat".
Your high idle speed is being caused by a vacuum leak. Your surging my be caused by a loose timing belt. A loose timing belt will cause the relationship between the crank and cam sensor to be off.
He had the timing belt replaced on another channel and it was done properly.
Timing belt loose both before and after swapping it? Chances of that are somewhat low imo.
A vacuum leak on a 30 year car would be expected.
Or Hall sensor is busted. Older Japanese cars has that problem pretty regularly. Error codes are indicative of that. Sometimes you cannot start engine at all but sometimes it works but poorly.
@@jakublulek3261 if the cam or crank sensor were busted the car wouldn't run.
If you want a weird (albeit not exactly modern) engine control system to discuss, the Bosch Trionic system in Saabs is my absolute favorite. Ionic knock detection through the spark plugs!
So these are just some little tidbits from an owner of a late 80s R31 Skyline, which also uses the ECCS computer (albeit with 6 cylinders to control), and while they may help you they probably won't fix all your issues. I'm just mentioning them as the "go to, first fixes" for Idle, timing, hesitation and surging, starting and power related inconveniences.
The screw on the ECCS unit does turn on diagnostics mode, but it also has some degree of idle speed control.
The Throttle Position Sensor can be rotated to adjust the idle->power and power->idle switching. Usually a handy fix for hesitation more than surging.
Putting a timing light on the car to see what degree of advance it has, and adjusting it may handle a variety of issues.
As for the IAC valve, as a general rule, never clean them with degreaser/brake clean unless you have to. Unfortunately even brake clean leaves a bit too much residue for the old valves. Carby/throttle body/MAF cleaner is the go. You can disassemble the IAC completely or just open it up and spray a bit in there. Depends how far you want to go.
The IAC should also have an adjustment screw on the back (at least thats where mine is). Combined the IAC, ECCS Idle Adjust/Diagnose screw, and TPS adjustment are the 3 ways the idle is generally controlled with an ECCS equiped engine.
As mentioned by a few others, definitely be on the hunt for Vac leaks, they cause many a headache.
Hope something helps. I love to see car stuff on non-car channels, I'm looking forward to seeing what you make of all this Suck-Squish-Bang-Blow business.
From memory the filaments in the MAF are powered all the time. When the filament is cold it's resistance is lower, so what is happening is that the circuit monitors the current trough the filament. One filament is sitting in the airflow and does the measurement. The other filament is not in the airflow and provides the reference so ambient temperature does not affect the readings. It will only see the difference between the filaments.
I work at an auto parts store. The MAF sensors are shockingly expensive. Especially for foreign cars. I definitely recommend that people try cleaning it first before replacing. $10 for a can of cleaner vs $200 for a new sensor you might not actually need. But when they go bad, it wrecks the performance and gas mileage of the engine, if it even runs at all.
-
Also expensive are the Oxygen Sensors, on average about $80-$120 each. When they go bad (and they go bad often, usually what turns on Check Engine Lights), it destroys your gas mileage as well. Thankfully a Check-Engine-Light scanner (OBD2) will tell you exactly which one is bad. (There's 2 sensors on 4 cylinder engines, and 4 sensors on 6, 8 and 10 cylinder engines.) You save money in the long run after replacing them, since you won't be getting 8 miles to the gallon anymore.
The 6BT 12 valve Cummins were 100% mechanical in the early 90’s. That’s where they made their name in the consumer market. The fuel injector pump was a miniature inline 6 motor that ran mechanically off of the engine.
Oh my goodness I would love a Technology Connections "History of Engine Control Systems" video -- and you're 100% correct, computers were already more common than people assume in the late 70s. Most of the early ones were "feedback carbs", which had all (or more) of the complexity with very little control. But there was a huge leap forward in technology during the 80s, and fuel injection went from being exotic to commonplace in only a few years. Carbs were practically eradicated in the US by 1990. I dunno if you read these things, but if you happen to see this, look up the Bendix Electrojector EFI from 1958 - you'll get a kick out of that!
On 90's Hondas that cold idle valve equivalent would cause surging as well. It was mainly for North American cars that can get a lot colder than cars in Japan. One "fix" was to block it off so it would operate as if it didn't exist, which was fine if you lived in an area that didn't go way below freezing.
Amazing you bought a Figaro! 👍
I've asked this question in one of your earlier videos: the 84 Corolla you spoke about, was that by any chance a GT-S or SR5 model? (AE86 or AE88)
I once had similar engine issues on a Land Rover Freelander. Slightly high and uneven idle, reluctant starting, and it was also running slightly rich, so when it failed on emissions at MOT test time, I had to fix it. It was a vacuum leak, but the leak was in the brake servo (I think you may call it the brake booster). I was sat in the car with the engine warm and idling, but noticed that when my foot was on the brake, the idle speed settled. It was almost imperceptible, but definitely there, and the effect was repeatable. I fitted a new brake servo more out of hope than expectation, and the change was a revelation. The engine ran sweetly, started promptly, and idled smoothly. Try putting your foot on the brake and see if your engine note or speed changes. You might even detect a hiss, but may have to stick your head in the footwell near the servo to find out. Blocking or squeezing closed the vacuum pipe to the servo (booster), to isolate that part of the system might help the diagnosis, but maybe don't drive without the brake assistance. Good luck!
An interesting video. Here in the UK I had a 1988 Nissan Sunny Coupe that still used a carburettor. Fuel Injection was reserved for the top of the range ZX models. An improvement over my 1979 car was that they had replaced the points with an electronic sensor in the distributor which triggered electronic ignition. Maybe that explains the position of the sensor.
Can confirm how this style of MAF sensor works. The PCM applies heat to the resistors shown, they're both heating elements. It will then monitor them to ensure they are at the correct temperatures. If they are *not* at the correct temperature, voltage will be applied or removed until it reaches that temperature.
The amount of voltage required to maintain that temperature is monitored and compared to a mapping table that tells the PCM approximately what amount of air is entering the engine through the intake system, assuming the intake system hasn't been tampered with beyond factory specifications (I.E. via putting a high-flow filter on or removing a resonator).
This system *sometimes* has the IAT sensor integrated as well, which might be the second resistor. (this will instead be a thermistor, which will usually also send a signal immediately upon key on to establish a base signal to go off of for starting) The IAT also effects this map since temperature also effects how quickly the resistor will cool and thus the effort required to keep it warm.
Both signals are used to reference each other, depending on make and model, since air flow will effect the IAT and cold or heat will effect the MAF.
There are multiple styles of MAF, this is just the one I know the most about.
If you’re looking for parts for this and cars like that - look to the North. Canada has a 15 year rule as opposed to the 25 year rule for importing so we see a lot of these cars up here, especially in British Columbia where it’s a quick boat ride from Japan.
There’s a whole cottage industry up here for parts and service for cars like this Figaro. A quick Google search should help, but search for companies like “Japanoid” who will have parts if you need them.
Are Nissan parts really that hard to get in the US? It's just a Micra with a different body on it. There must be millions of these engines still on the road in Europe.
Here are the possible problems that cause the the idle speed and starting problems: vaacum leak, stuck pcv valve, stuck idle control valve, air intake temperature sensor (if equipped), throttle position sensor and last but not least o2 sensors. But it wouldn't hurt to check the throttle cable for binding or misadjustement for the high idle speed if all else fails and a fsm will help out a ton to test all the parts mentioned above so you don't throw parts at it.
I appreciate this. You're not some mad car nut spouting stupid phrases and part names no one else gets if they're not already a car person. You're making this simple enough that most people can get it.
Imagine a American-French engine computer from 1987 used in a major automotive brand that is completely ahead of it's time, but also fairly crude.
I introduce the Renix system for AMC Jeeps, it has a reliable heated O2 sensor, multi spark ignition system, sequential fuel injection, and yet no way to store engine faults unless you hook it up to a rare engine diagnostic reader that was only available to dealers. It's 4WD and A/C systems are operated by a series of vacuum motors through out the vehicle. Also the automatic transmission for the 4.0L engine is controlled via computer. Had wireless key entry, and yet no power seats.
It's amazing how mine is even working today.
I enjoy all of your videos, but it is really neat to see you working on and appreciating a gasoline engine driven car as well!
Cool video! I'm a mechanic of 36 years and would love to see more follow up videos on this car. Don't know why but it intrigues me.
Glad to hear your plans for main channel vids. More car related videos please!
Automotive Technician here. As others have said, check for vacuum leaks, not just from vacuum lines but even things like the manifold and throttle body gaskets, throttle shaft, all of the valves connected to the intake, even the brake booster. On that age of car, things break down, and the fact that it is turbocharged puts all those parts on the intake under more strain. Also, check the intake hoses, intercooler piping and even the intercooler itself for leaks/splits.
Also, another idea to throw out is the coolant temperature sensor. I can't remember if Robert replaced that or not, but Nissans have an issue with poor connection at this sensor. It can be a problem with the sensor or the connector or both. If the sensor fails or the resistance caused by a poor connection skews the ECT sensor reading enough to make it inaccurate but still be within normal range, it will not set a fault code. This is one of the biggest difference between older EFI and modern EFI systems, the self-diagnostics. On older EFI systems (when working with 5V sensors) as long as the sensor voltage is between about 0.05-4.95V, it will be considered to be OK by the ECM and it will use the sensor reading even if it is completely inaccurate, because it isn't programmed to do anything else. Modern cars will compare like sensors to see if their readings are plausible, even if they are all "within normal range," i.e. if your car sat overnight (known as a cold soak) all the temperature sensor should be pretty close to each other. If you ambient air temp, intake air temp, engine oil temp, transmission oil temp sensors all read 70 deg after sitting overnight but your engine coolant temp reads 150 deg, this would be considered OK by an older OBD system but would likely set a plausibility fault on a newer OBD system.
(side note, in the industry to have a saying, "NEW stands for Never Ever Worked." Don't assume that a part is working properly just because it is new, especially if it is an aftermarket part)
The reason I bring up the coolant temp sensor is because, aside from it being a common issue on that era of Nissan, its one of the few sensors used during initial start-up. Aside from the newest low emissions vehicles and hybrids, many engine sensors are ignored during start-up because cranking emissions weren't really a big deal until just recently. While cranking and for a second after the engine starts, most of the timing and fuel calculations are all done from really basic look-up tables in the ECM, and really the only modifiers for that come from battery voltage (low battery voltage increases injector latency, so the pulse width needs to be increased if the battery voltage is low), throttle position (mainly used to shut off the injectors on many cars if the throttle is wide open), and the intake air and coolant temp sensors (cold engines need more air and fuel to start in order to overcome the tendency for the gasoline to condense on cold parts, liquid gasoline doesn't burn). The engine speed sensor (usually the crankshaft position sensor, but on older cars with a distributor they usually only have sensors in the distributor for engine speed) is also used but usually just for ignition since again, the timing of the fuel injection isn't critical just to make the engine start. The coolant temperature sensor has arguably one of the most important roles in how well you engine starts, because it pretty much single-handedly determines what fuel mixture the ECM is attempting to deliver during cranking. The particular starting issue you are having seems more like a cranking mixture issue to me because it runs poorly immediately after it starts. Typically if you have something like a MAF issue or a vacuum leak, it will start fine and run ok for a second before it either starts to run like poo or stalls out. I'm also concerned about the ECT sensor reading because of the high idle. Cold engines need more air and usually will have a higher cold idle. Some older cars did this mechanically by either using a fast-idle valve with a wax motor in them that is heated up by the coolant or by using a wax motor to push the throttle linkage open when cold, but in other cases, it is done electronically either with vacuum switching valves (solenoids) or an idle air control valve. If the ECT sensor reading is cold all the time, it could cause this issue.
Anyway, I'm rambling now, but hopefully you'll find some of this info useful.
I recently bought a 2003 Generation 1 Prius, which has SIX interconnected computers, two electric motor-generators, fly-by-wire throttle and brakes, electronic power steering, and a freaking TOUCHSCREEN! Pretty crazy for a car that was originally released in 2000!
The timing advance is still done inside the distributor, it's has electronic ignition that eliminated the need for points and condenser but still has mechanical advance in the distributor
I know it’s late and not sure if it’s been suggested yet but, any small air leaks between the throttle body and MAF can skew reading to the ECU and it will behave like a faulty or dirty MAF sensor.
Check for any loose hose clamps in the intake ductwork and pay close attention to the rubber & plastic parts to be sure there’s no cracks or dry rotting, even the slightest crack will make engine performance suffer.
30 years isn’t kind to plastics and especially detrimental to many types of rubber parts.
Essentially un-measured air is entering the engine but it wasn’t accounted for by the MAF and it fools the ECU which causes a whole bunch of starting and drivability/performance issues.
70s engine computers were indeed a thing! Look up the Chrysler Lean Burn system. When it worked it went OK but it was definitely not for performance. When it broke, nobody knew how to fix it and a lot of people gave up and installed a conventional ignition system and in the case of later feedback carb systems, a conventional carb as well. Yes...electronic feedback carburetion, the stuff of nightmares.
The temperature sensor that was replaced, was it the ECU coolant temp sensor or the temperature gauge sensor?
I don't know the details of this particular system, but early Bosch based systems had a 5th injector, used during engine cranking. If your car has one, you will find there is another "sensor" on the engine near the main coolant temperature sensors. This is a time delay switch that is activated during cranking, it is temperature dependent. The purpose of the switch is to operate the 5th injector to provide cranking enrichment and provide after start enrichment for a certain time period, if it fails you will experience difficult starting and the engine won't stabilise for maybe 10-15 seconds under certain conditions.
This system is probably new enough that they got rid of that feature though and the computer will just increase the injection duration of the normal 4 injectors during cranking.
Yeah I remember similar little buzz boxes like these zipping around Osaka. Not this old but the updated versions.
Other similar models are also very popular with drifters and the street racing community as they have a very high power to weight ratio, and qualify for a yellow plate, which results in far cheaper technical checks.
As far as the MAF operation. Usually a "hot wire MAF" sensor interanlly measured the current required to keep the wire at a given temperature. More airflow required more current to maintain that temperature.
The two symptoms you described sound like they can both be attributed to the ECU getting the wrong coolant temperature reading. This can often be caused by air in the cooling system--which does result in surges on some cars as the coolant temp reading will fluctuate because coolant is splashing on it instead of it being submerged.
I'm not sure if this engine has an idle air control valve (IACV), but definitely worth investigating. The valve tends to get dirty and begins to hang up from time to time, causing your engine to have a difficult time maintaining idle. If your Figaro engine does have one, usually you can locate the IACV, access the air inlet port, spray some throttle body cleaner in there and allow it to soak the valve within to help loosen up some of the deposit buildup. After a few minutes, start up the engine and see if anything improves.
Sometimes this method works; other times you are replacing the valve. Again, this is just speculation on if you actually have one. Also, it wouldn't hurt to pull the intake tube off and see if you need to clean the throttle valve. Usually there's carbon/deposit buildup on the throttle valve, which again, can affect idle conditions. Some easy things to check either way.
That boxy TPS may be a throttle position _switch_ rather than a potentiometer-type sensor. Those old switches could be a bit finicky and require either adjustment or internal cleaning. They're a 3-position, on-off-on switch; you adjust them by rotating the TPS with a continuity tester attached so that one pair of contacts _opens_ just off idle, usually around 200 RPM higher. The other side isn't adjustable, just make sure it _does_ close at some point within the throttle's operating range.
They modify the fuel map at idle and under heavy load, so being out of adjustment can definitely affect your idle.
You're correct - the ECU has no control over the idle air valve. It's simply a rotary valve that's actuated by a bimetallic strip, with an electric heater in it. When the key is in the 'run' position, +12V is put to the two-pin connector on the valve and it begins to heat up. When cold, the valve allows bypass air past the throttle plate, allowing for a 'fast' idle position. As it heats up over the course of thirty seconds or so, the heated bimetallic strip rotates the valve shut, so no bypass air is allowed.
This valve remains powered and heated as long as the car is running, which is why they fail as often as they do.
There are three other idle-control circuits on the Figaro that you need to consider as well:
- There's an idle-air solenoid on the rear of the intake manifold that raises the idle speed when a pressure sensor on the power steering system reads that you're cranking the wheel over
- There's an idle-air solenoid on the front of the intake manifold that raises the idle speed slightly when the headlights are on, to compensate for the extra load of the alternator
- There's another idle-air solenoid next to that one which raises the idle speed when the air-conditioning is set to 'on'. Note that this doesn't necessarily mean the compressor clutch is engaged; this circuit will be energized when the dash panel is set to A/C on, regardless of the compressor state
There are two adjustment screws that adjust the bleed air past each of the last two solenoids. Those are located under the black plastic caps on the idle-air block mounted to the front of the intake manifold. Each of those screws seal in the block with rubber o-rings that are likely ossified by now.
The FIgaro's idle air system is painfully simple - there's no dynamic adjustmet. It's literally some bypasses and bleeds to kick the idle up on command, and all of them need to be dialed in.
Also (also!) it's time to pull the intake air boot from the MAF to the resonator box, from the resonator box to the turbo inlet, and from the turbo to the throttle body look for cracks that will allow unmetered air in. I managed to kill my first Figaro by running it lean due to a crack in the articulated rubber section post-MAF allowing in unmetered air and causing it to run lean.
If you haven't yet, it's probably a good time to pull the valve cover and ensure that the rocker shaft is torqued down correctly as well.
Figaro Owners' Club has instructions on how to adjust the idle properly, and The Figaro Shop sells a complete set of silicone intake hoses, as the original Nissan pieces went out of production sometime during the Clinton presidency. Best of luck with your Figaro. Hopefully you didn't do what I did and buy your from Gary Duncan ;)
Beautiful display cluster in the dashboard.
That is in really beautiful condition for a 30yr car, especially a rust belt car. Absolutely mint.
Had some fun finding an engine problem in my 150 PS 1.9 JTDm Alfa 159 as well, that also covered the MAF. Yours is as clean as it can be. But if you're unsure, Ebay is a good source for all kinds of stuff you cannot find anywhere else. An A/B test can help sometimes to determine the actual source.