Stalling on start up - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72timemachine · 09-04-2025, 12:43 PM

Hello,

I went to restart my 1990 Chevrolet c2500, 5.7 ltr. the other morning (engine was already hot) as I left the store parking lot only to have it stall once I started the engine. At first I was not sure what was going on because this never happened before. I literally had to ride the brake to keep the engine from stalling at red lights and stop signs.

After driving a few miles, I pulled over to see how the engine would idle and while it seemed a bit low, it did not stall and from this point up until now, it has been starting and idling fine. My question is, could this be the idle air control valve acting up or perhaps the throttle positions sensor?

Thanks for any help ahead of time.

RustyPile · 09-04-2025, 01:33 PM

Don't start guessing and certainly don't start throwing parts at it.. Follow an organized troubleshooting procedure.

A check engine light will alert to engine management issues.. Is your check engine light on?? A problem with either of the items you mentioned will set a trouble code and turn on the check engine light.

72timemachine · 09-05-2025, 12:01 AM

The last thing I want to do is guess, hence my inquiry in this forum. I'm not Mr. Goodwrench but I'm not exactly inept either. I feel the stalling issue was so brief that it did illuminate the check engine light so that is why I was asking if this may have happened to any of the other members and what they may have found the problem to be.

I of the opinion that if it happens once, it typically will happen again and may get progressively worse over time so I would rather not wait on this if I can proactive and fix the problem.

I understand that even if an engine light is illuminated on the dash and you find a code on the OBD 1 system, it does not mean that is the exact cause of the problem, more like something else acting up which may have triggered the problem. An example could be something such as a simple vacuum hose leaking, however, the ecm is unaware there is a vacuum leak and continues to add fuel to keep the stoichiometric air/fuel ratio in check.

I have done a basic visual all around the throttle body looking for anything like a loose or broken vacuum line, the throttle body bolts are still tight and new cylinder heads and gaskets were installed last year. My truck has never run better or smoother since I did this work but all of a sudden that happened the other day so I would like to know if anyone else has experienced this and were they able to find out what the cause was.

I do have a new AC Delco fuel pump as of two years ago and I measure the inline pressure with correct inline adapter and I had a reading of 11 pounds at the time. The fuel filter is only a year old and I drive less than the average per year. The timing chain was replaced and when you turn the crank and look at the rotor on the distributor, it is still hardly any slack in the chain. I do not beat on my engine.

My distributor has a new pickup coil, module and ignition coil as of last year when that all went out. The cap and rotor are in good condition with no visual cracks, carbon tracking or excessive wear. The AC Delco plug wires are fairly new and show no damage to the outer insulation and are secured with wire separators and zip ties where needed.

RustyPile · 09-06-2025, 02:57 AM

I'll address your first paragraph..

I'm pretty close to being a "Mr. Goodwrench", as I'm a GM trained Drivability Technician. Engine stalling and low idle speed is a very common complaint. I've had my hands on hundreds of vehicles with that issue.. But I must tell you, for that one complaint, there are numerous solutions.. Stuck EGR valve, Stuck or dirty IAC valve. Defective logics in the computer, faulty or missing RPM signal, Coolant temp sensor... The list goes on and on..

Within your dissertation, not one word about a trouble code or check engine light being on. A scan tool, a code chart, and a troubleshooting flow chart are aids for deciphering those items.. Here's a link to an example of a flow chart..

https://www.bing.com/search?q=GM+tro...ANAB01&PC=LCTS

As to your 3rd paragraph: Since you don't have much faith in check engine lights and trouble code accuracy (probably due to your lack of knowledge of how the system works), that's about all I can do towards helping you..

09-04-2025, 12:43 PM	#1
72timemachine Registered User Join Date: Oct 2008 Location: los angeles ca Posts: 223	Stalling on start up Hello, I went to restart my 1990 Chevrolet c2500, 5.7 ltr. the other morning (engine was already hot) as I left the store parking lot only to have it stall once I started the engine. At first I was not sure what was going on because this never happened before. I literally had to ride the brake to keep the engine from stalling at red lights and stop signs. After driving a few miles, I pulled over to see how the engine would idle and while it seemed a bit low, it did not stall and from this point up until now, it has been starting and idling fine. My question is, could this be the idle air control valve acting up or perhaps the throttle positions sensor? Thanks for any help ahead of time.

09-04-2025, 01:33 PM	#2
RustyPile Registered User Join Date: Dec 2017 Location: Elkhart, Texas Posts: 2,108	Re: Stalling on start up Don't start guessing and certainly don't start throwing parts at it.. Follow an organized troubleshooting procedure. A check engine light will alert to engine management issues.. Is your check engine light on?? A problem with either of the items you mentioned will set a trouble code and turn on the check engine light.

09-05-2025, 12:01 AM	#3
72timemachine Registered User Join Date: Oct 2008 Location: los angeles ca Posts: 223	Re: Stalling on start up The last thing I want to do is guess, hence my inquiry in this forum. I'm not Mr. Goodwrench but I'm not exactly inept either. I feel the stalling issue was so brief that it did illuminate the check engine light so that is why I was asking if this may have happened to any of the other members and what they may have found the problem to be. I of the opinion that if it happens once, it typically will happen again and may get progressively worse over time so I would rather not wait on this if I can proactive and fix the problem. I understand that even if an engine light is illuminated on the dash and you find a code on the OBD 1 system, it does not mean that is the exact cause of the problem, more like something else acting up which may have triggered the problem. An example could be something such as a simple vacuum hose leaking, however, the ecm is unaware there is a vacuum leak and continues to add fuel to keep the stoichiometric air/fuel ratio in check. I have done a basic visual all around the throttle body looking for anything like a loose or broken vacuum line, the throttle body bolts are still tight and new cylinder heads and gaskets were installed last year. My truck has never run better or smoother since I did this work but all of a sudden that happened the other day so I would like to know if anyone else has experienced this and were they able to find out what the cause was. I do have a new AC Delco fuel pump as of two years ago and I measure the inline pressure with correct inline adapter and I had a reading of 11 pounds at the time. The fuel filter is only a year old and I drive less than the average per year. The timing chain was replaced and when you turn the crank and look at the rotor on the distributor, it is still hardly any slack in the chain. I do not beat on my engine. My distributor has a new pickup coil, module and ignition coil as of last year when that all went out. The cap and rotor are in good condition with no visual cracks, carbon tracking or excessive wear. The AC Delco plug wires are fairly new and show no damage to the outer insulation and are secured with wire separators and zip ties where needed.

09-06-2025, 02:57 AM	#4
RustyPile Registered User Join Date: Dec 2017 Location: Elkhart, Texas Posts: 2,108	Re: Stalling on start up I'll address your first paragraph.. I'm pretty close to being a "Mr. Goodwrench", as I'm a GM trained Drivability Technician. Engine stalling and low idle speed is a very common complaint. I've had my hands on hundreds of vehicles with that issue.. But I must tell you, for that one complaint, there are numerous solutions.. Stuck EGR valve, Stuck or dirty IAC valve. Defective logics in the computer, faulty or missing RPM signal, Coolant temp sensor... The list goes on and on.. Within your dissertation, not one word about a trouble code or check engine light being on. A scan tool, a code chart, and a troubleshooting flow chart are aids for deciphering those items.. Here's a link to an example of a flow chart.. https://www.bing.com/search?q=GM+tro...ANAB01&PC=LCTS As to your 3rd paragraph: Since you don't have much faith in check engine lights and trouble code accuracy (probably due to your lack of knowledge of how the system works), that's about all I can do towards helping you..



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