My 1991 gmc with 454 stalls when you stop and has a real choppy idle that ranges from 1000 rpm down to stalling. How do I fix that? Is it a computer issue?

indicates a vacuum leak or idle speed sensor problem
may fix by increasing the idle rpm to around 800-950 rpm

Hello Patricia Kennedy.

Besides a dirty air filter... listed below... idle air control valve... the idle speed is pretty tamper proof...

If the car has not been tuned up RECENTLY... that would be a STRONG recommendation before fine-tuning the idle speed.

The problem I am seeing ALL OVER the web... is the idle is too fast... (absolutely will cause STALLS).

All things being reasonable... your tachometer should show an RPM OF 650 to 1000 rpm... above that is quite EXCESSIVE...

A real TUNE-UP MANUAL would be required to properly set the SPEED ... but only after EVERYTHING had been serviced, cleaned and replaced...

Tuning up a car with DIRTY FILTERS & WORN spark plugs is an WASTE of MONEY!!

What I am seeing EVERYWHERE... is a HIGH IDLE problem... (above 2000 RPMs... That will ABSOLUTELY cause your car to stall at a STOP... because your TORQUE CONVERTER is designed to lock up (quit acting like a clutch)...

If your idle speed it above 1000 rpm... that WAS a BIG RECALL issue for GM engines...

Check out the links below... a high idle can stall an engine better than a low one...!!

Comment me back if I am not being particularly clear... or wwatch some of the videos I have attached.

Good luck.


More Information for ACDELCO A1208C
2005 buick rendezvous idle setting Bing video More Information for STANDARD MOTOR PRODUCTS AC5T

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Mar 10, 2010 - My fiancee's '99 Accord EX Coupe 4-cylinder automatic, with 130,000+ miles, has recently (in .... No low RPM & feeling like it's GOING TO stall.

99 Honda Accord - Strange Stalling Issues! HELP!

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My 1999 Honda Accord is having sporadic stalling problems. I've noticed a pattern. Itstalls while going slow speeds and stop and go traffic, etc. The engine just ...

Stalling or Low Engine Idle Speed Due to Dirty ... - Repair

I had an 86 that used to do that all the time and I replaced the starter and then it worked fine

Idle air control (IAC) control rpm idle during idle.

Test it on idle with ALL electrical on full force.
RPM should increase.
If RPM remain the same then IAC is question.

Do you have the idle speed turned up to keep it from dying? Because it is high. Check engine light on? Have you checked for vacuum leaks at the gasket under the throttle body? How does the car run under acceleration? You might have a worn distributor shaft.

Probably IAC that controls the idle. If so you will see or hear idle go up and down some and can definitely lead to stalls

I would go down to your local auto parts store and do an alternator and battery test. It sounds like at low rpms you are loosing volts. When you apply the brakes you would be supprised how much power from the engine it takes. You could also be loosing oil pressure. Check your oil level. When your engine drops low rpm, the oil pressure drops and shuts down the engine.

near the throttle body there is an adjusting screw(flat head) for air fuel mixture, it's on a deep cavity sometimes with a cover, adjust counterclockwise will increase the idle.

I had problems with the idle and with the car stalling and found that it was a failed oxygen sensor. I replaced it and the car runs great now.