Observations: black smoke out tailpipe. upstream O2 sensor not cycling completely, reporting lean. TPS a little high. Fuel trim negative(!) Why? Normal coolant temp signal. downstream sensor swinging a but MORE than expected if cat is working properly. First thing would be to get more history, has any work been done on vehicle? In the back of my mind I've considered the outside possibility the upstream and downstream sensors are accidentally swapped. Or perhaps somebody fiddled with the throttle idle screw. The thing that jumped out at me was the negative fuel trim, which doesn't fit with an under-reporting sensor by itself. This leads me to consider the possibility of two diagnoses, or perhaps a computer that has used substituted values because it thinks the O2 sensor data is not reliable. With black smoke out the tailpipe and negative fuel trim values, the engine is running rich and the computer is trying to compensate by reducing fuel. One inadequate explanation would be a stuck open injector on one cylinder, causing a rich situation which should push the O2 sensor up, causing the PCM to shorten injector pulse width, resulting in a negative fuel trim and maybe random misfires. However here we have low sensor readings, so it's not so simple! If the O2 sensor was under-reporting then I wouldn't expect the PCM to react by cutting back fuel, unless it is responding to data on the opposite bank and using substituted values from there. Or, perhaps the rich cylinder is on the opposite bank, causing correction on the bad side and a secondary lean on the good side.... Suppose the MAF is dirty, underreporting air intake. The computer would start out delivering less fuel, and normally the O2 sensors would then recognize a secondary lean condition and start adding fuel, so fuel trim should be positive, not negative. But if the MAF was underreporting AND the O2 sensor was giving spurious high values you might get this pattern. However O2 sensor values on that bank are low, not high. Not a great fit there, unless the primary response was on the other bank. Suppose a cylinder has an electrical misfire, like an intermittent shorted coil or wire. Fuel would pass through that cylinder and drive the O2 sensor up, which again should force a lean condition on all the other cylinders. Again, no explanation for why the O2 values are too low, unless perhaps the problem is on the other bank and you're seeing the unopposed effects on this bank. Suppose the cat and the O2 sensor have been damaged by a chronically rich situation, such as leaking rings or bad compression. The O2 sensor could send bad data, not recognizing the extra oil in the exhaust, ultimately being destroyed and failing lean. The clogged cat could cause many of the same symptoms. This one seems the most likely to me.... I'd pull that O2 sensor and put a pressure gauge in the hole to measure back pressure from the cat. I'd double check the wiring to the sensor to see if there is any physical way the two sensors could have been swapped. I'd look a little more closely at the TPS PID to verify that it does change with position of the gas pedal. I'd put the secondary ignition on a labscope to see if there are any more clues as to how this is happening. And I might do a quick relative compression test before spending a lot of money on investigations! Thanks, Duane, glad to see you back!
Spelunkerd, that is a great response. The title to the video is "an exercise in critical thinking" your response is great example of just that. You have covered so many possibilities and they are all good. I like the way you "think" instead of "guess". I hope everyone reads your reply. Thanks for sharing it. I think you'll enjoy the next 2 parts. They'll be posted soon.
I will said a clog catalytic convertor. The back pressure is stuck in the area of the o2 sensor making the o2 sensor read lean but before to change the cat. I will be sure that my maf and map are working properly even without a code a dirty maf or map can give a lot troubles. Saying this I will remove the o2 sensor and I will do the torch test just to be sure that my sensor is good and I will be check the back pressure in the muffler.
Yes another learning series I love these!!! I'll have to agree with the TPS assessment from others. Scan tool reported it went up to 1994 RPM but TPS value only changed from 22% to 27%. Sounded like he mashed on that pedal to open the throttle more than 5%. Plus, 22% angle during idle? That would be abnormal for my car. I'd want to verify integrity of TPS. If TPS is off then ECU would have a field day trying to compensate using only the MAF and O2 data. I never get these things right though, can't wait to find out and learn more. :)
Honestly I'm thinking that it's a bad O2 sensor (or perhaps a high resistance wiring/connection issue) that's making it report lean and drowning bank 1 with fuel to the point of causing a misfire. If it were me, I'd be giving the wiring to said O2 sensor a good look, and if no obvious issue seen, then replace the O2.
Larry Bolan, I agree I would test the wiring and the o2 to either rule it out or condemn the o2 but would have checked to make sure I did not have a fuel issue.
Here is my amateur hour, non professional thinking (I'm in accounting/it) Visual indicators are that the car is running rich (black smoke). This would be consistent with the bank 1, sensor 1 O2 oscillating low (not going above .5v) due to presence of raw fuel making its way out of cylinder. O2 sensors analyze Oxygen content, not fuel content so unburned fuel would actually lower the amount of oxygen in exhaust and cause O2 to report lean. This is also borne out by the bank 1, sensor 2 O2 reporting rich by showing a fluctuating yet abnormally high value close to .9v. Raw fuel is making it to cat and getting burned and producing a lot of oxygen. From my understanding, when a cat is going bad, the upstream and downstream O2's oscillate in similar pattern and similar range. That is not happening in this case. S1 O2 is switching low, S2 is switching high. This makes me think cat is still operating (albeit perhaps not for long with raw fuel making its way to it). Car is bogging down because of too much fuel in chamber. The P0300 is a random misfire code and not cylinder specific which makes me think it is not a leaking injector which I would think would throw cylinder specific code; but perhaps rather a ruptured fuel pressure regulator (assuming not returnless) or evap saturation issue. I don't know anything about an Uplander (never even heard of one before this video) but also assume it only has 2 O2 sensors and not 4(?) - otherwise we would see same issue in both banks including error codes for second bank. Only thing that does not match normal operation is the fuel trim values being negative. Computer is pulling fuel away because it is detecting a rich condition even though upstream O2 is reporting lean. For this i would have to guess that spelunkered is correct that computer is detecting a bank 1, sensor O2 error so ignoring it as an input. Perhaps seeing B1S2 reporting rich so using that as part of fuel strategy(?). This may be reason why computer can't fully compensate for rich condition via fuel trims. they are "only" lean around 12 - 15%. Lot's more can be taken away but computer doesn't have reliable inputs to detect. Though it seems as B1S1 O2 is working correctly. Either way, rich condition is not being caused by engine computer but by some other faulty system. Where to go from here? To me there are only a couple places a rich condition can be coming from. So a quick check of fuel pressure regulator, evap lines for normal operation. And finally if both are good, then look at injector wave form patterns for normal operation make sure one is not stuck open. Has to be one of the 3 offhand...though my early money is on fuel pressure regulator. Cure cause of rich condition first, then revisit rest of system. My $.02. Looking forward to seeing next few vids and how my initial analysis stacks up. Thanks for posting - i really like these multipart interactive case study videos.
O2 Sensor, wire to him(bad connectors) or ECM. Test wire first after unplug a connector to the O2 sensor and connect to the battery which has 1.5 volts. If you see more then 0.9 volts on the scanner - replace O2 sensor, if less then 0.9 - replace the ECM.
Potentially multiple issues here. Let's first address the O2 sensor as a good sensor will help diagnose if there is an additional problem causing a lean condition. Check the O2 sensor circuits (power, signal, heater, and ground) and connectors to ensure the proper voltage and amperage are passing to/from the O2 sensor. Check the Ohms measure on the heater element to ensure continuity. Once the O2 sensor problem is identified AND fixed - circuit, connector, or Sensor itself - also look to see if there is still a lean condition to address. If so, use the O2 sensor feedback to help indicate what might be causing the lean condition - fuel delivery, vacuum leak, exhaust leak, etc.
Bad O2 sensor - because B1S1 is not fluctuating, however, since the engine is in closed loop it's taking input from it and dumping more fuel in which is resulting in the black smoke. However, B1S2 (after cat) is showing rich (correctly) which is what the STFT and LTFT are trying to correct.
No one notice that the tps was reading 22% @. 622rpm?? That's a lot higher than I'd expect to see. Also, when he rev'd the engine, it never exceeded 27%. Coolant tempt sensor is reading 194 which isn't alarming after the engine warmed up. My next probe would be towards the TPS.
I've seen Many a VW with symptoms similar to this. 9 times out of 10 when you pull up the live data like shown here, you'll find a coolant temp sensor reading -22° on a miserably hot Florida day. The computer thinks the car is in the arctic circle and floods the engine with gas. 😂😂 Clearly not the case here, though.
I am disagree with the tps sensor. My explanation that tps doesn't move more of 27% is because you are reading a lot data in the same screen even the tps open more of 27% the scanner is too slow to show it.
I'm more lead to a bad cat. If you guys notice the reading of the o2 bank 12 it is changed from .46 to .86 with the engine already warm. This is a clear sign that the cat isn't doing his job properly
A misfire will give give out un burnt gas and oxygen from the intake. The upstream 02 sensor only sees the oxygen and says the mixture is lean and meanwhile the unburnt gas continues on through the cat and burns up with the oxygen where the downstream 02 sensor detects a rich mixture as shown by the black smoke. Both sensors are functioning correctly. This argument sounds plausible but there again so does all my arguments. I think it's time to put on the kettle and have a cuppa tea and clear the head.
The propane test would make me feel better. If there is no way you can get that sensor to go above .6 volts or so then it has to be the O2 wiring or the ECU. I would unplug the signal wire and touch one hand to positive on the battery an other to the signal.wire on the ECU side and check for a higher voltage on the scan data.
Next reset pcm and scope the b1 upstream O2 sensor at the connector to make sure the readings are the same to what the pcm is seeing if they are different then scope the o2 at pcm to rule out bad wiring or pcm Note Downstream o2 is reading rich .8v
If you really have a lean problem both of the O2 sensors will read lean, but the B1S1 read lean and the B1S2 is switching normal, so to me the problem is the oxygen sensor.
Thank you for the presentation. It was well explained. I'm not a seasoned mechanic/technician but one area we haven't discussed is what is the engine temp sensor reading? If it's sending information to the ECM that the engine is cold, the ECM would think it needs to deliver more fuel. Looking forward to part two.
wyattoneable yes but like you said the computer will be add more fuel because think that is too cold but in this case the computer is subtracting fuel.
Oscar Turrunrojo no crees que si fuera problema de fuel delivery los dos sensores de oxigeno del mismo banco estubieran dando casi el mismo voltaje? Si te fijas uno siempre esta a menos de .4v lean y el otro entre .7v y .9v rich
When investigating the O2, rather than just changing it, it would be a good idea to not only test the sensor, but the wiring to it. No sense changing out the sensor, if, for example, an open in the wiring was causing the low voltage....???
I think the next step would be to look for a restriction in the cat. The back pressure would affect the bank one sensor and the restriction would effect the rear sensor reading. If the cat was ok I would look for an air leak after the maf sensor. The computer is not picking up the leak because its after the sensor so the air to fuel mix is off and giving a lean code.
Ron Baynes If the computer didnt see the vacuum leak it would have never thrown a lean code. If its after the MAF sensor then the MAP and upstream sensor would help to identify it. In other words the computer did see a vacuum leak, hence why the lean code is there.
Hello Sir .Can you tell me if the STFT and LTFT digits are correct on my vehicle? .idle STFT = oscillations between -2.3 a + 2% . LTFT = always 0%! Do you think these are good corrections ? a guy tells me that there may be a vacuum leak! But a vacuum leak would still have numbers in the positive in idle! is it possible to have a very slight leak at the intake manifold gasket, without interfering in the fuel correction in idle, but see the numbers change by passing a cleaning spray brakes around the intake manifold gasket? Thank you in advance
those numbers look normal to me, but they can change at idle or under a load. Discuss it with someone locally who can watch them when the engine is runnung
realfixesrealfast ok thank you very much 👍 it's a Ford Focus RS MK2, with pcm remapped and big injectors 650cc etc .... Stage 3 415hp and 610nm on the power bench!
jstow98 f although it could be a bad o2 sensor. The misfire shouldn't be there the computer will go on limb mode if a bad o2 sensor running relative smother
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Thinking voltage drop occuring on the signal feed out of the o2 sensor to the ecu. Either from a high resistance wire /connectoe or ecu pin
Observations:
black smoke out tailpipe.
upstream O2 sensor not cycling completely, reporting lean.
TPS a little high.
Fuel trim negative(!) Why?
Normal coolant temp signal.
downstream sensor swinging a but MORE than expected if cat is working properly.
First thing would be to get more history, has any work been done on vehicle? In the back of my mind I've considered the outside possibility the upstream and downstream sensors are accidentally swapped. Or perhaps somebody fiddled with the throttle idle screw.
The thing that jumped out at me was the negative fuel trim, which doesn't fit with an under-reporting sensor by itself. This leads me to consider the possibility of two diagnoses, or perhaps a computer that has used substituted values because it thinks the O2 sensor data is not reliable. With black smoke out the tailpipe and negative fuel trim values, the engine is running rich and the computer is trying to compensate by reducing fuel. One inadequate explanation would be a stuck open injector on one cylinder, causing a rich situation which should push the O2 sensor up, causing the PCM to shorten injector pulse width, resulting in a negative fuel trim and maybe random misfires. However here we have low sensor readings, so it's not so simple! If the O2 sensor was under-reporting then I wouldn't expect the PCM to react by cutting back fuel, unless it is responding to data on the opposite bank and using substituted values from there. Or, perhaps the rich cylinder is on the opposite bank, causing correction on the bad side and a secondary lean on the good side....
Suppose the MAF is dirty, underreporting air intake. The computer would start out delivering less fuel, and normally the O2 sensors would then recognize a secondary lean condition and start adding fuel, so fuel trim should be positive, not negative. But if the MAF was underreporting AND the O2 sensor was giving spurious high values you might get this pattern. However O2 sensor values on that bank are low, not high. Not a great fit there, unless the primary response was on the other bank.
Suppose a cylinder has an electrical misfire, like an intermittent shorted coil or wire. Fuel would pass through that cylinder and drive the O2 sensor up, which again should force a lean condition on all the other cylinders. Again, no explanation for why the O2 values are too low, unless perhaps the problem is on the other bank and you're seeing the unopposed effects on this bank.
Suppose the cat and the O2 sensor have been damaged by a chronically rich situation, such as leaking rings or bad compression. The O2 sensor could send bad data, not recognizing the extra oil in the exhaust, ultimately being destroyed and failing lean. The clogged cat could cause many of the same symptoms. This one seems the most likely to me....
I'd pull that O2 sensor and put a pressure gauge in the hole to measure back pressure from the cat. I'd double check the wiring to the sensor to see if there is any physical way the two sensors could have been swapped. I'd look a little more closely at the TPS PID to verify that it does change with position of the gas pedal. I'd put the secondary ignition on a labscope to see if there are any more clues as to how this is happening. And I might do a quick relative compression test before spending a lot of money on investigations!
Thanks, Duane, glad to see you back!
Spelunkerd, that is a great response. The title to the video is "an exercise in critical thinking" your response is great example of just that. You have covered so many possibilities and they are all good. I like the way you "think" instead of "guess". I hope everyone reads your reply. Thanks for sharing it. I think you'll enjoy the next 2 parts. They'll be posted soon.
I will said a clog catalytic convertor. The back pressure is stuck in the area of the o2 sensor making the o2 sensor read lean but before to change the cat. I will be sure that my maf and map are working properly even without a code a dirty maf or map can give a lot troubles. Saying this I will remove the o2 sensor and I will do the torch test just to be sure that my sensor is good and I will be check the back pressure in the muffler.
Yes another learning series I love these!!! I'll have to agree with the TPS assessment from others. Scan tool reported it went up to 1994 RPM but TPS value only changed from 22% to 27%. Sounded like he mashed on that pedal to open the throttle more than 5%. Plus, 22% angle during idle? That would be abnormal for my car. I'd want to verify integrity of TPS. If TPS is off then ECU would have a field day trying to compensate using only the MAF and O2 data. I never get these things right though, can't wait to find out and learn more. :)
Honestly I'm thinking that it's a bad O2 sensor (or perhaps a high resistance wiring/connection issue) that's making it report lean and drowning bank 1 with fuel to the point of causing a misfire. If it were me, I'd be giving the wiring to said O2 sensor a good look, and if no obvious issue seen, then replace the O2.
Larry Bolan, I agree I would test the wiring and the o2 to either rule it out or condemn the o2 but would have checked to make sure I did not have a fuel issue.
The O2 sensor is lying, change it! Many thanks, sandy
I'd like to fuel pressure and vacuum readings. Simple and cheap to complicated and money is my way. I need more evidence.
I really like your videos that force us to think and troubleshoot, can't wait for pt 2
Here is my amateur hour, non professional thinking (I'm in accounting/it)
Visual indicators are that the car is running rich (black smoke). This would be consistent with the bank 1, sensor 1 O2 oscillating low (not going above .5v) due to presence of raw fuel making its way out of cylinder. O2 sensors analyze Oxygen content, not fuel content so unburned fuel would actually lower the amount of oxygen in exhaust and cause O2 to report lean. This is also borne out by the bank 1, sensor 2 O2 reporting rich by showing a fluctuating yet abnormally high value close to .9v. Raw fuel is making it to cat and getting burned and producing a lot of oxygen. From my understanding, when a cat is going bad, the upstream and downstream O2's oscillate in similar pattern and similar range. That is not happening in this case. S1 O2 is switching low, S2 is switching high. This makes me think cat is still operating (albeit perhaps not for long with raw fuel making its way to it). Car is bogging down because of too much fuel in chamber.
The P0300 is a random misfire code and not cylinder specific which makes me think it is not a leaking injector which I would think would throw cylinder specific code; but perhaps rather a ruptured fuel pressure regulator (assuming not returnless) or evap saturation issue. I don't know anything about an Uplander (never even heard of one before this video) but also assume it only has 2 O2 sensors and not 4(?) - otherwise we would see same issue in both banks including error codes for second bank.
Only thing that does not match normal operation is the fuel trim values being negative. Computer is pulling fuel away because it is detecting a rich condition even though upstream O2 is reporting lean. For this i would have to guess that spelunkered is correct that computer is detecting a bank 1, sensor O2 error so ignoring it as an input. Perhaps seeing B1S2 reporting rich so using that as part of fuel strategy(?). This may be reason why computer can't fully compensate for rich condition via fuel trims. they are "only" lean around 12 - 15%. Lot's more can be taken away but computer doesn't have reliable inputs to detect. Though it seems as B1S1 O2 is working correctly. Either way, rich condition is not being caused by engine computer but by some other faulty system.
Where to go from here? To me there are only a couple places a rich condition can be coming from. So a quick check of fuel pressure regulator, evap lines for normal operation. And finally if both are good, then look at injector wave form patterns for normal operation make sure one is not stuck open. Has to be one of the 3 offhand...though my early money is on fuel pressure regulator. Cure cause of rich condition first, then revisit rest of system.
My $.02. Looking forward to seeing next few vids and how my initial analysis stacks up. Thanks for posting - i really like these multipart interactive case study videos.
O2 Sensor, wire to him(bad connectors) or ECM. Test wire first after unplug a connector to the O2 sensor and connect to the battery which has 1.5 volts. If you see more then 0.9 volts on the scanner - replace O2 sensor, if less then 0.9 - replace the ECM.
Potentially multiple issues here. Let's first address the O2 sensor as a good sensor will help diagnose if there is an additional problem causing a lean condition. Check the O2 sensor circuits (power, signal, heater, and ground) and connectors to ensure the proper voltage and amperage are passing to/from the O2 sensor. Check the Ohms measure on the heater element to ensure continuity. Once the O2 sensor problem is identified AND fixed - circuit, connector, or Sensor itself - also look to see if there is still a lean condition to address. If so, use the O2 sensor feedback to help indicate what might be causing the lean condition - fuel delivery, vacuum leak, exhaust leak, etc.
First off, B1S1 is not showing accurate, if you compare with B1S2. My first move would be to change sensor 1. Cheers.
Bad O2 sensor - because B1S1 is not fluctuating, however, since the engine is in closed loop it's taking input from it and dumping more fuel in which is resulting in the black smoke. However, B1S2 (after cat) is showing rich (correctly) which is what the STFT and LTFT are trying to correct.
No one notice that the tps was reading 22% @. 622rpm?? That's a lot higher than I'd expect to see. Also, when he rev'd the engine, it never exceeded 27%. Coolant tempt sensor is reading 194 which isn't alarming after the engine warmed up. My next probe would be towards the TPS.
I've seen Many a VW with symptoms similar to this. 9 times out of 10 when you pull up the live data like shown here, you'll find a coolant temp sensor reading -22° on a miserably hot Florida day. The computer thinks the car is in the arctic circle and floods the engine with gas. 😂😂 Clearly not the case here, though.
Can we get an KOEO full sweep of the throttle? I'd like to see what the TPS' range is reading.
Good eyes!
I am disagree with the tps sensor. My explanation that tps doesn't move more of 27% is because you are reading a lot data in the same screen even the tps open more of 27% the scanner is too slow to show it.
I'm more lead to a bad cat. If you guys notice the reading of the o2 bank 12 it is changed from .46 to .86 with the engine already warm. This is a clear sign that the cat isn't doing his job properly
lazy 02 sensor, like you said, a normal 02 switches between .1 .2 up to .8 or .9 this b1s1 is bad. the engine is fully warmed up in closed loop.
Haven't seen enough data to nail down a definitive diagnosis. Verify o2 wiring and TPS full range with KOEO.
Defective wiring, bad ground connection (many times a reason causing problems) or, at the very end, a malfunctioning sensor.
A misfire will give give out un burnt gas and oxygen from the intake. The upstream 02 sensor only sees the oxygen and says the mixture is lean and meanwhile the unburnt gas continues on through the cat and burns up with the oxygen where the downstream 02 sensor detects a rich mixture as shown by the black smoke. Both sensors are functioning correctly. This argument sounds plausible but there again so does all my arguments. I think it's time to put on the kettle and have a cuppa tea and clear the head.
The propane test would make me feel better. If there is no way you can get that sensor to go above .6 volts or so then it has to be the O2 wiring or the ECU. I would unplug the signal wire and touch one hand to positive on the battery an other to the signal.wire on the ECU side and check for a higher voltage on the scan data.
Next reset pcm and scope the b1 upstream O2 sensor at the connector to make sure the readings are the same to what the pcm is seeing if they are different then scope the o2 at pcm to rule out bad wiring or pcm
Note Downstream o2 is reading rich .8v
I had a problem like this... in a 99'ram. I had bad intake gaskets upper and lower plenum also a bad upstream o2 sensor.
I think is a clog cat, because it is bogging and the sensor not working properly damaged the cat.
If you really have a lean problem both of the O2 sensors will read lean, but the B1S1 read lean and the B1S2 is switching normal, so to me the problem is the oxygen sensor.
I agree. Wouldnt condemn the sensor with out checking the wiring though. I believe its an issue with the o2 sensor wiring
I'll have to look at the mass airflow readings could be a dirty mass airflow sensor
Bad wiring of O2 sensor. It's being pulled to ground
this is an old video. its been uploaded years ago. pcm fixes it
Exhaust leaks can be nasty and will display these exact symptoms.
I would look at the temp sensor pid and make sure it isn't at -40
Thank you for the presentation. It was well explained. I'm not a seasoned mechanic/technician but one area we haven't discussed is what is the engine temp sensor reading? If it's sending information to the ECM that the engine is cold, the ECM would think it needs to deliver more fuel. Looking forward to part two.
wyattoneable yes but like you said the computer will be add more fuel because think that is too cold but in this case the computer is subtracting fuel.
how about a vacuum leak from a weak gasket somewhere or hose somewhere?
Have you tried reticulating the splines?
The theists should implement this type of thinking
Great video, thanks for your hard work.
I would say it's the O2 sensor.
bomba de gasalina con alta precion o regulador de combustible roto o sensor de precion de gasolina fuera de rango
Oscar Turrunrojo no crees que si fuera problema de fuel delivery los dos sensores de oxigeno del mismo banco estubieran dando casi el mismo voltaje? Si te fijas uno siempre esta a menos de .4v lean y el otro entre .7v y
.9v rich
When investigating the O2, rather than just changing it, it would be a good idea to not only test the sensor, but the wiring to it. No sense changing out the sensor, if, for example, an open in the wiring was causing the low voltage....???
I also believe that as an O2 fails, it fails rich to protect the engine, which would explain the black smoke out of the exhaust.
I think the next step would be to look for a restriction in the cat. The back pressure would affect the bank one sensor and the restriction would effect the rear sensor reading. If the cat was ok I would look for an air leak after the maf sensor. The computer is not picking up the leak because its after the sensor so the air to fuel mix is off and giving a lean code.
Ron Baynes If the computer didnt see the vacuum leak it would have never thrown a lean code. If its after the MAF sensor then the MAP and upstream sensor would help to identify it. In other words the computer did see a vacuum leak, hence why the lean code is there.
you are good proffessor
Hello Sir .Can you tell me if the STFT and LTFT digits are correct on my vehicle? .idle STFT = oscillations between -2.3 a + 2% .
LTFT = always 0%! Do you think these are good corrections ?
a guy tells me that there may be a vacuum leak! But a vacuum leak would still have numbers in the positive in idle!
is it possible to have a very slight leak at the intake manifold gasket, without interfering in the fuel correction in idle, but see the numbers change by passing a cleaning spray brakes around the intake manifold gasket?
Thank you in advance
those numbers look normal to me, but they can change at idle or under a load. Discuss it with someone locally who can watch them when the engine is runnung
realfixesrealfast ok thank you very much 👍
it's a Ford Focus RS MK2, with pcm remapped and big injectors 650cc etc .... Stage 3 415hp and 610nm on the power bench!
tps is not moving
O2 sensor!
Vacuum leak?
Lazy o2 sensor.
I'd still check heater circuit. then power and ground, Then ref voltage before calling the sensor bad.
jstow98 f although it could be a bad o2 sensor. The misfire shouldn't be there the computer will go on limb mode if a bad o2 sensor running relative smother
clogged cat on that bank?
i dont like these type of videos i may not have time to watch the next video or forget and i dont learn anything make one video for the whole fix
You could set up notifications for his videos and get an email when the next one comes out.
Please never stop making videos. You are an amazing teacher with a ton of experience. Thank you for all your great videos and lectures!