Engine stalls at idle?

Tiny
DSPLACE2007
  • MEMBER
  • 1994 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 254,000 MILES
Hi, my 1994 chevy 2500 v8 K vin 5.7 liter stalls at cold idle and while driving, but esp when I first crank it up cold. I had this prob a couple wks back and it sent code 35 IAC valve. With throttle body exposed the TB makes loud hissing sound, as if vacuum leak or starved of fuel. Then when this sound goes away, the vehicle runs. I can run up to whatever speed, say 60 mph last night down highway and boom, vehicle dies. Started back up and got it home. This morning, same hissing and stall over and over, then ran fine, then stalled. Not sure IAC valve could cause this vehicle to stall like this at idle or driving at higher rpm. Hope that is what it is though. I disconnected fuel line and tested fuel flow and filter, and it seems that fuel flow is vast. Could it be a fuel pressure regulator, or intermittent fuel pump issue? I tested map sensor, and ignit module and they test fine. Spark or fuel, I don't know, or even a sensor? The hissing at TB is what puzzles me though. When it runs fine, hissing gone, then comes back and boom, vehicle stalls out. Could it be relay? I cannot find a fuel pump relay on this at all. I am just wondering why it sent code 35 IAC valve though. Could that cause vehicle to die at all speeds and idle? Maybe it is a weeks fuel pump. Prior to this problem, a day or two before, I ran out of fuel due to fuel gauge being inoperative. Please help as I would like to be able to see my little boy and girl. Thanks.
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Sunday, September 14th, 2008 AT 2:31 PM

41 Replies

Tiny
2CEXPT
  • MEMBER
This guide can help us fix it

https://www.2carpros.com/articles/stall-at-idle

Here's how to clean the IAC valve:

Disconnect the air intake ductwork from the throttle body.

Start the engine, then increase and hold the idle speed to 1,000 to 1,500 rpm.

Spray the throttle cleaner or engine cleaner into the throat of the throttle body, aiming for the idle air bypass port (usually located on the side or top of the throttle body opening). Give this area a good dose of cleaner (about 10 second's worth).

Turn the engine off to allow the cleaner to soak into the IAC passageway.

Wait about three minutes.

Restart the engine, rev and hold at 1,000 to 1,500 rpm, and repeat the cleaning process again.

Turn the engine off again, and reattach the air intake ductwork to the throttle body.

Start the engine and rev and hold to 1,500 to 2,000 rpm until no white smoke is coming out of the exhaust pipe.

If this fails to make any difference, you can remove the IAC valve from the throttle body and spray cleaner directly on the tip of the valve and/or into the ports in the throttle body. Let the cleaner soak awhile, repeat as needed, then reinstall the IAC valve, start the engine and run it at 1,500 to 2,000 rpm as before until no white smoke is seen in the exahust.

If the idle speed still surges after this, the IAC valve is defective and needs to be replaced.
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Wednesday, February 27th, 2019 AT 12:46 PM
Tiny
JOKER4U
  • MEMBER
  • 1993 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 230,000 MILES
I bought this truck and installed a crate motor in it. I have had a problem with the idle loping and engine turning off at stops since I have had it running. (30k mile) I have installed new plugs, wires, fuel pump, map sensor, fuel pressure regulator, idle control sensor. I am at my end with this. If you have an idea I'd be ecstatic to fix it. It's about to become someone else's problem. I've had numerous mechanics look at it and no success. I have had gm products for 30 years but I'm done with government motors! Please help if you can. Thanks
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
HMAC300
  • EXPERT
See if the gasket below the tbi unit has blown use choke cleaner then check the hose leading to map sensor for being soft ifit is replace it. As it may be sucking together I am assuming all timing stuff is correct. Then make sure tbi unit is spraying correctly sometimes they lose contact on top.
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOKER4U
  • MEMBER
The gasket below the tbi is brand new and all bolts are tight. No leaking. Both injectors are making good contact.
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
HMAC300
  • EXPERT
Ok a couple thing I forgot, check canister pruge vavle it may be open at idle and shouldn't be. It should have vacuum on one side only at idle if it h as vacuum going through valve then that may be your problem also if fuel filter hasn't been changed try that as well. Also check )2 sensor for silicone on it as that screws it up so it gives a crappy reading to the pcm and it leans mix out. Same with purge valve being open. Also check egr for blockages and egr valve for being stuck open. The canister purge valve is red.
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOSH71411
  • MEMBER
  • CHEVROLET SILVERADO
I have a 1993 chevrolet silverado with a 4.3l v6 vin code "z" the mileage is 198,789 if my truck is idling


http://www.2carpros.com/forum/automotive_pictures/102442_IM000223_1.jpg

with the a/c on and in gear and i turn the wheel my truck wants to stall it doesnt die but almost does then the rpms will pick back up until the wheel is turned again i have tried everything i think if anyone has some help i would really appreciate it
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
BMRFIXIT
  • EXPERT
The rpm drop not being compensated for by the idle air control
check it and check the air way for it make sure its clean and free of carbon
good luck
let us know
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOSH71411
  • MEMBER
I have already replace the idle air control valve and no improvement
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
DENNYP
  • EXPERT
Try cleaning the throttle body and spraying a good carbon cleaner in the throttle body with the enging running. I would recommend "sea foam" or "GM top engine cleaner".
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOSH71411
  • MEMBER
I have already cleaned the throttle body for about an hour still no improvement any more suggestions
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JAMESBROWN
  • MEMBER
  • 1993 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 101,000 MILES
Truck dies at idle when a/c is on
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOSH71411
  • MEMBER
I seriously need help on this problem its driving me crazy I dont know what it is I think I have replaced just about everything it only wants to drop idle when the wheel is turned with the air on and in gear if truck is in park its not as bad but still stalls when the wheel is turned so I dont think it is a torque converter problem I have replaced the idle air control valve so I think it maybe a power steering pump of steering gear please help !
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
2CEXPT
  • MEMBER
The computer might not be getting the input signal to raise the idle when the compressor engages thru the IACV-could be an idle up solenoid problem or the curb idle speed is too low. Try raising it and see what happens.
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
BMRFIXIT
  • EXPERT
Let s start fresh
Running ok steering fine put AC on wants to stalls when steering
Rpm ok @ idle and in drive engine running strong
AC on wants to stall when turning
Here what I m thinking?
Check the AC pressure hi side

Good luck
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOSH71411
  • MEMBER
Ok so I need to ask a few questions before I do this I believe u know something I dont but what would the high side have to do with the problem and how would I check the high side I have a set of manifold gauges but im new at a/c and also what would I be looking for
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
HVACMAN
  • MEMBER
  • 1990 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 133,000 MILES
My truck will not stay running. I can start it but it will only run for about 3 seconds then dies. I can keep it running for a short time by preesing the pedal. I have changed fuel filter, module inside distr. I have good cones of fuel while running.(TBI )
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
BMRFIXIT
  • EXPERT
You did just about every thing else
Just another idea
hook the gauges up and read the high and the low side s
If the high is too high that may be putting drag on the engine
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
SCOTTY DEE
  • MEMBER
Check for vacuum leaks with some Berrymans or propane. Especially around the t-body and intake gaskets.
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOSH71411
  • MEMBER
What should the high side pressure be
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
BMRFIXIT
  • EXPERT
I don t have the spec on that but I would say no more than 260
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Thursday, September 3rd, 2020 AT 6:37 PM (Merged)

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