I have this wierd problem that i cant seem to figure out. The idle seems to surge up and down about 200 rpms but only in reverse and drive, if i move it to park and neutral it steadies out.

ALso noticed when this happens the wide band seems to swing from 10 to 16 or so and back and forth

alos sometimes just turning the car off and starting it back up will stop it...


anyone come across this b4?

 

I have they exact same problem. I cant figure it out either i thought it was the timibg i checked nf time is right on. Also is my TPS. Im out of ideas. Hopefuly someone can help us out.

 

I'd check and clean the IAC valve. It's on the bottom of the throttle body and controls the amount of air getting to the engine at idle.

While you have the throttle body off, I'd go ahead and clean it as well. Just use some of the simple spray cleaners you find at any parts store. The gunk will usually come right off.

 

i think its actually a ecm problem. considering sometimes just turning the car off and restarting it will fix it

 

check this out

 

I had the samething happening on my 87 IROC. I replaced all the vaccum lines and the issue went away.

 

My alternator just gave out two days ago i replaced it and it helped my idle issue but its not fully gone which leds me to believe it might be an injector or electric problem i.e wires,plugs or bad ground is it possible for a ground to cause this. Also i noticed yesterday i was messing with it a bit i did the minimum air adjustment i left the rpms a bit higher than stock and it helped the idle issue. Could this mean its a fuel related issue?. My timing is dead on 6*.