YACT: Starts then almost stalls after being driven awhile

[alm99]

Its a 1996 Saturn SL2 with 113K

The problem: The car starts up and idles down fine when it has been sitting for awhile(3 to 4 hours), overnight, etc. Its when you turn off the car to run inside or go to the store for just a short time. The car will start rev up to ~2000 RPMs and then just drop to 500 or 600RPMs and almost stall, then it revs back up to ~1300RPMs and then either drops to normal idle 800RPMs or stalls completely. When waiting at a light the car will sometimes idle below 800 RPMs and seems to have a tough time running. Also when you are going slow <15 mph and coming to a stop, the car will drop in RPMs and almost stall, it has yet to stall doing this though.

Any thoughts on what this might be?

 

[Vortex22]

*pulling something out of my ass*

Fuel pump?

 

[alm99]

I was thinking vacuum leak, but I don't know.

<---- Has no clue

 

[Bryophyte]

I'm certainly no car expert, but when I had a problem like this with my VW Fox way way back in college, it turned out to be a plugged fuel injector. Added fuel injector cleaner once or twice, drove fine afterwards.

 

[alm99]

I may have to give that a shot

 

[alm99]

up for some more opinions

 

[Thegonagle]

Hi.

That sounds like a symptom of a bad Idle Air Control Motor (or similar name with the words idle, and air in it). It?s a servo mechanism that receives a signal from the ECU to keep the idle speed constant, regardless of the load from A/C, automatic tranny, etc., by admitting more or less air into the engine.

If it's malfunctioning, the engine will idle erratically.

 

[conjur]

Vapor lock? Try a different brand of fuel. Do you typically use 87 octane? Maybe bump up to 89 (Super Unleaded wouldn't help out, really).

Or...as others have said...a bad O2 sensor or idle control.

 

[Ornery]

I think you'd need to invest in a Service Manual to even come close to figuring that out. Our 1988 E-150 with 5.0L FI has a special low idle solenoid (or valve, or motor, or something like that) controlled by one ,two, or three sensors and or module(s). Needless to say, it gets turned over to a mechanic with a computer to troubleshoot that kind of wondrous, high tech hoo-hah.