I have an 89 IROC-Z with a 305 with 120K miles and a five speed manual. When I star up the car, the car idles fines and the engine sounds strong. After the car warms up, the car begins to idle poorly. The whole car vibrates and you can actually see the engine shaking under the hood. Once you put in gear, the car feels real smooth and the engine is strong through all the gears until the next red light. A mechanic told me that I need to replace the throttle body. I think it may be something else and don't want to spend money unless it will fix the problem. Has anyone had the problem or does anyone what could be wrong. Thanks in advance for any help.

 

ok well i can try to help, see my timing was a little too advanced or retarded, i dont kno but what happened was, i took it for a ride around the block, and it ran fine until it warmed up. then, every time i floored it it would show signs of a timing issue, but when i was returning, i got it to the bottom of my driveway, and it stalled out. when i started it back up it idled horribly. it has a big cam in it, but this was worse then normal, as if it werent running on all cylinders. if i were you, i would loosten the 9/16th bolt holding down the destributor,then rotate the destributor ever so slighty counter clockwize, while it is running. that ended up fixing my problem. your idle will most likely go higher then normal, so you might have to lower the idle down a little. i would try this method first, because you can simply turn it back if its not the case, no harm will be done.

 

Thanks for the reply. I'll try that first chance I get to work on my car. One thing though. My car is TPI. Is it possible to adjust the idle on a TPI engine? I've heard that the IAC controls that and you can't adjust it.

 

Thats true, you can't adjust the idle on a TBI motor. The IAC motors are known to fail on occasion. That would screw up your idle only. Open the throttle and the IAC does nothing.

 

Dose'nt the ECM also controll timming as well? On a 2.0 '86 Cavalier I had I just set base timming and the comp did the rest. Sometimes you can remove the IAC and clean the carbon buildup out of it and cure the problem. I've done that on a few Jeeps and older fuelie GM cars at work, worked every time.