91 GMC C3500 TPS and IAC Replacement High Idle
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- Опубліковано 1 лис 2024
- Replacing the TPS and the IAC on the 91 GMC C3500. Engine is a TBI 454 7.4 big block. Idle seemed a bit to high all the time.
Things that might help with a project like this:
AC Delco TPS: amzn.to/2Ud6VHE
AC Delco IAC: amzn.to/2DZL1Sj
AC Delco Throttle Body Gasket: amzn.to/2Sp6Fn1
This video contains affiliate links, which means that if you click on one of the product links and buy, I'll receive a small commission.
Things that might help with a project like this:
AC Delco TPS: amzn.to/2Ud6VHE
AC Delco IAC: amzn.to/2DZL1Sj
AC Delco Throttle Body Gasket: amzn.to/2Sp6Fn1
This video contains affiliate links, which means that if you click on one of the product links and buy, I'll receive a small commission.
I've had the a/c request give high idle. The heater/ac controller can fail internally and send an a/c request but the compressor doesn't come on. IAC can't lower idle so it will flag it as faulty. Carry on, enjoy the videos.
A common issue on the slightly newer trucks is he actual 4 wires going to the IAC. I have a special noid light that fits and will show if he circuits are ok. A good tug on he wires can help to. It appears they use the same style back in 91 Enjoyed the video thanks for sharing as usual.
That is interesting. The A/C flashes on the heater control sometimes. When the battery is unhooked it works normal again. But the idle is still a little high with it working fine.
I might have a vacuum leak somewhere.
Rod Adams Thanks! Have a 94 454 chevy truck. Went a-z, seen your comment and switched ac/heat controller (used from another truck). Idle went down to proper 750/800ish when in gear.
when my A/C kicks on I have the opposite issue, the RPMs don't compensate for the additional load
I just replaced my EGR valve, had to remove the IAC to get to it. Now my truck idles way high! I wonder if I damage the IAC. It's a 93 gmc 5.7 422,222 miles!
Give this a try ua-cam.com/video/6zzdBKSKBgc/v-deo.html
If the idle still gives you issue's, make sure the voltage is in the .58.59 range on the data logger, I work a lot on these gen 1's. Thank you for the great content sir. Great lookin truck.
Not sure I have an idle issue. It's idling at 900rpm. That seems high to me but I saw a 454ss idling at 900 too.
mossman381, Maybe just a touch high for minimum idle speed. I like to set target idle around 750-800 rpm's.
Is there a way to adjust it? The computer controls the idle. Not sure what .58 and .59 on the data logger means. I haven't had one of these older trucks for a long time. Any help is appreciated.
mossman381, Yes of-course my man. You can utilize a cheap OBD1 scan tool, or use a DRL to back probe the dark blue wire for voltage readout that goes to the TPS, you want it between .58-.59 volt range. You may need to enlarge the two little bolt holes on the TPS sensor itself if the engine has been modified. I had to do such on my dads rig. You can also get an adjustable TPS on amazon. Try this great website for info pertaining to what you are doing. Best of wishes an luck to ya sir. www.gmcmidwestclassics.org/Web%20pages/Tuning%20the%20TBI.pdf
G Man hey I got a question my idle is really bad and I'm told I need to fully rebuild my tbi cause it's running rich I'm told all sensors IAC tps fuel pressure regulator injectors coolant temp sensor etc
Just had the bolt break off when replacing the TPS on my 1990 suburban. Just made a simple job complicated
That's the way it goes with old trucks.
change the coolant temp sensor while you are at it it does have a function at the tb
A CTS can tell the computer that it's Winter when really it's Summer. A code tester with live test can check that like the Actron CP9690.
Hey man. When the throttle position sensor went bad, would you have to crank the truck twice to get it to start? Cuz that's what I'm having to do with my 97 k2500 7.4. I was talking with a friend of mine and he told me it sounded more like the throttle position sensor. I at first thought it was sparkplugs
Not really sure. Without looking at it myself. Your 97 is a bit different than this truck. It would have the fuel injection not TBI. If it's and easy job and a cheap part it probably worth a shot. If the truck has not had a major tune up in a very long time (Distributor cap, rotor, wires, plugs even coil) it might be a good time to do it. You could also check fuel pressure. Seems like the fuel pressure regulator can be an issue with those trucks.
looking for help with a problem. 2000 chevy2500 with 5.7 liter Truck will intermittently have low power like its missing, or not getting fuel. Going to try and replace fuel filter (assuming its on the frame rail), first, but someone mentioned something inside the distributor could be the problem. Any suggestions? When it happens, truck still runs but will idle at lower RPMs, and when trying to accelerate, it bogs and hesitates, feels like it has low power. Then it just magically goes away and truck goes back to normal. Not related to temperature....does it when engine is hot or cold, same for outside temps...no consistency. ?? if fuel filter isn't the problem I'm guessing plugs or wires next, but looking for other ideas.
Distributor cap, rotor, plug wires, spark plugs and fuel filter. Maybe even the coil if you have the funds. These are all tune up parts that should be done if you think the truck has not had any of them changed before. I am guessing the truck has high mileage so those parts will only help it run at it's best. I am not sure where the fuel pressure regulator is on those trucks but that could be a problem.
Hello I found that the accelerator cable will stick or jam just before a dead standing idle causing high idle
i replaced the iac fuel pump fuel filter spark plugs spark plug wires ignition coil .. cap and rotor . tps and egr and still my truck high idles and burns alootta gas then dies not too sure if its the timing thats off and or the gas regulator is fucked too cuz when u step on the brake it dies. as well
Does the exhaust smell like gas? I didn't see oxygen sensor in your parts list. Have you checked your tps voltage? I have a video on that as well. Mine idles a little high but I think that is a tbi thing. Once warm it's decent. The 454 isn't easy on gas but not that bad.
mossman381 yes smells like gas quiet a bit and idles high appreciate the feedback btw ✌👍👍yeah havnt done the oxygen sensor . but honestly dont hav the tools to do any of that voltage stuff or timing and to be specific i hav a v6 4.3 chvy but i assumed its similar cuz its a tbi
That is a vacuum leak.
i believe the two iac they used is the one you have and the other had threads on it and takes a 15/16 wrench to remove
I have seen the screw in type. Might actually be the better than two very small bolts.
yes they are i too have snapped those bolts no how careful you are no mater how much you spray them they brake
So did you solve the high idle problem?
After adjusting the TPS and a new O2 sensor the truck run a lot better. I also had a plug wire that had come off and I didn't know.
Had a 98 Chevy Tahoe had a really bad high idle and had really bad performance when driving how to get a valve job cost about a grand
I just replaced my idle air control valve. It still idles rough. What could it be?
Bad fuel, fuel filter, injectors, spark plugs, distributor cap/rotor, plug wires. I would do what they call a major tune up which will replace most of those items. O2 sensor could be the issue. Vacuum leak is common with old hoses. Throttle body gasket bad. Many things could be causing your issue.
Hey I'll be in wisconsin for the 4th of july any chance i'd be able to buy that truck off you? Always wanted a 91 white dually
We will have to see this summer if I still have it or if I want to sell it then.
mossman381 Alright. I will be staying in Sturtevant
I have a 1989 gmc sierra k1500 350 tbi and my Speedometer, odometer, oil pressure gauge and coolant temp gauge do not work and my check guages light stays on even after I changed the Moonie gauge cluster out for another Moonie cluster
If they are all not working you might have a ground issue or something wrong with your plug. Without looking at it myself not sure what to tell you.
Who else can see the crack under the mounting point for the egr valve
omg yes🚗
timestamp?
I hope you get it figured out. Pesky little issues like that will keep you busy right?
It's about more than the high idle. This is a 454 big block. I want it to run as efficient as it can so no fuel is wasted. This thing will drink the fuel anyway. These newer parts will help it run better even if they didn't solve the idle problem. I will figure it out eventually.
Intake gasket? Tbi's are known for it
Could be.
good luck gettn ur $ back, they changed there policy about electrical components. once out of store its urs. u must no someone if u do get ur $ back
Non
What size pintle
Not sure what you are asking.
mossman381 the diameter of the iac pintle..they come in two different sizes..10mm and 12mm
In the video, I could go back and verify..but I vaguely remember you saying about how there were only 2 or 1 and you hoped it was the right one..something like that, but I'm surprised you didn't measure the diameter of the pintle of the iac..that little round tip at then end..they have two options and they differ in size
One guy said there was two different types for my truck. Another guy said there was only one. This one has worked good so far. I can look and see if I have the part # but I probably threw the box away.
@@davepolynice3811 Yes they do. Be sure and measure the old one before replacing.
Replaced iac now it idles high
Maybe give it some time to adjust. When you are dealing with these old vehicles it can be multiple things that are bad/old. If you haven't replaced the O2 sensor that really helps these older trucks.
Man you love throwin parts at trucks!!!
It's not about throwing parts at it. The parts on the motor are 26 years old and have had who knows how many heat cycles. Parts may still work but they aren't working at there best. I have no issues replacing parts on an old vehicle. This is a 454 big block that I want running as efficient as it can. It can't do that with old slow sensors. Call me a parts changer but you won't find me on the side of the road ever. The new parts might cost more up front but when you aren't on the side of the road and don't need a tow truck they more than pay for themselves. And all these parts are notorious for going bad on these engines.
Carry on my bloodline??????? I think you are watching the wrong channel.
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