Stalls At Idle

[Marccus]

My '89 (302,000 mi) stalls when I take my foot of the throttle and the rpm drop below about 1,000.

I was taking an off ramp after driving 40 mi @ 65 mph, down shifted, then started braking after putting it in neutral, when the car stalled. I tried to make the 90 degree turn at the bottom of the ramp through a yellow and just barely got the car turned by man-handling the steering.

It starts up fine and runs fine, but as soon as I release my foot from the throttle and the rpm start falling it stalls. If I start it up and just keep my foot on the throttle so the engine runs above 1000 rpm, it's fine - until I take my foot off the throttle whereby the rpms drop and it stalls again. :banghd:

I've had a problem with the CEL for about a year when it would intermittantly come on for sometimes several seconds or minutes then go off. If I turned the car off when the check engine light came on, the CEL would be off.

There are no codes so bottom line is I can't trust the CEL. :cuss:

I DID wash the engine compartment yesterday but it ran fine after that and it ran fine all morning during my 40 mi drive to work. I've washed the engine compartment down many times during the 16 years I've had the car, but I'm always careful about keeping water off connections, etc, using baggies. Alll my connections are sealed with adhesive heat shrink tubing and lots of dielectric grease to keep moisture/water out.

I did check the "taughtness" of the throttle cable briefly and it seemed "loose". Could the throttle cable have "slipped" from either end slightly so that when there is no pressure on the pedal, the throttle is "shut" instead of being opened to the idle position?

If so, perhaps I can just adjust the throttle body screw.

Also, does the throttle body cable wear out and need replacing sooner or later or is this a "lifetime" part?

Any ideas?

 

[NiNeTy Fo SHO]

From the sounds of it, I would be checking the IAB (idle air bypass valve)

It sounds like the car runs pretty stout except when it is trying to idle on its own. The IAB lets air in to keep the car idling.

I wouldnt think its the cable...the throttle body should be in the closed position when your foot is off the gas...and the IAB takes care of the idling. My IAB didnt throw a code either.

Autozone and the like will check the part for correct working order for free if removed from the car...2 bolts and 1 wiring harness.

 

[Marccus]

Thanks for the concise reply, chief. Sounds good and it makes sense. Thanks for setting me straight on how the idling works - I should have known better!

I'll check it out during lunch.

 

[NiNeTy Fo SHO]

Good luck sir! hope all goes well

 

[JLT1787]

Your cats are probably clogg full of carbon

 

[Marccus]

Why would they be clogged with carbon?

Did I do something that would cause this or is this something that happens after so many miles? :banghd:

I have the PP high flow cats and installed them about 100,000 mi ago - I think?

If they are clogged, how do I unclog them or do I need new cats?

 

[shospeed143]

A clogged cat will cause a rough idle to so by the way it sounds it is something with the IAB like what NiNety Fo SHO said. You might be able to clean the passages for it to see if that will help. If you have a volt/ohm meter you can test the IAB by disconnecting the connector. Then putting the red lead of the ohm meter were the red wire connected to the IAB, then the black wire onto the other one. If the resistance is not between 7-13 ohms replace the IAC.