I have an 88 c1500 chevy with the 4.3l tbi. It has been excellent to me until recently.
It started with random high idles. It wasnt constant. Every now and then id be at a light or something and it would suddenly rev up to around 1600-1800rpm. Id take off and notice that my 'shift' light would act funny. It would stay on when i wasnt in gear (its the 5 speed manual) and also stay on with my foot off of the gas while in gear. It didnt throw a code at all.
Then it started throwing a code 21 at idle when it idled to high i checked the tps and it was working perfectly fine, around .48v to 5v or so, if i remember correctly and it was smooth increase and decrease.
It drove fine for a few days.
Then it started idling high much more ofter and stall while driving down the road in gear and i let off the gas. Thats when i got the code 22 as well as the code 21. Its stalling out now in gear whether or not im on the gas and idles high almost frequently. My check engine light goes on and off sporadically. Ive che ked the tps a few times now and still its where it should be.
I have a feeling that its my ecu but i have now way to tell.
Any ideas to what could be causing this?
I rebuilt the throttle body about 3 months ago and replaced the old tps and ia. Along with new injector pod.
Any help is much appreciated.