Hello all, I've recently picked up a 90 5.7 GTA, it is my 9th TPI motored car I have owned so I'm pretty familiar with these engines however I am stumped with this one, basically the car stalls when putting in gear from Park, the rpm's drop below 500, it will also stall at a stop. The car starts right up when putting back in Park. If I unplug the IAC valve the car does NOT stall however it idles too high of course. Another issue is when in Overdrive at low speeds there is a hesitation shifting into 4th if the trans in in Drive there is no hesitation, it also seems to do it worse when the engine is cold, I'm not sure if these are two seperate issues or related any help would be greatly appreciated before I start throwing parts at it.

 

Some more info on the car, it was recently tuned up at Pep Boys with AC delco plugs, and aftermarket wires, and cap&rotor, I just changed the pcv valve and fuel filter with AC delco. The IAC motor was replaced several years ago with an AFTERMARKET one so that is what I'm considering replacing next possibly? The fuel pressure seems perfect at 43psi, I have not checked timing yet and the SES is not on UNLESS after driving for a while so that may be EGR valve? The transmission was rebuilt about 10kmi ago. I have cleaned the throttle body with CRC cleaner and it made a HUGE difference power wise(it was a dog when I bought it) but did not fix the stalling and hesitation...

 

My car did this for the longest time, I finally had an oh **** moment, and capped my EGR valves vacuum port. Hasn't had an idle problem since. That's where I'd start. Cap it and see what happens. Also before replacing the IAC, pull it and clean it. It can get carbon build up that will prevent it from working properly. Just spray it with throttle body cleaner, making sure that you hold it so it doesn't drip into the motor itself.

 

Thanks for the reply, I figure just to replace the IAC with an AC delco one ($75) instead of cleaning the old one and if that doesn't fix the stalling and erratic idle going through the trouble of two installs etc..if I cap the EGR won't I have to get a new PROM?

 

I've heard some people have the ses light come on, but it personally hasn't caused me any problems at all.

 

Do you think the hesitation in Overdrive is EGR related? There is no hesitaion/sputter at higher speeds so I don't think it's the converter or internally the transmission TCC solenoid maybe or ignition related maybe?

 

I think it's probably a separate issue, but handle one issue at a time.