WHY MY CAR WILL NOT IDLE CONSISTENTLY on 1991 Chevrolet Camaro

I HAVE REPLACED THE IDLE AIR VALVE, TPS, AND WENT THROUGH THE STEPS OUTLINED IN THE MANUAL TO RESET THE IDLE BUT IT STILL DOES NOT ALWAYS IDLE THE SAME. ONE TIME IT WILL IDLE RIGHT THE NEXT TIME IT IDLES TOO FAST, THEN TOO SLOW. SOMETIMES TOO ROUGH. I TRIED TO CLEAN OUT THE THROTTLE PLATES BUT MAY NOT HAVE DONE A GOOD ENOUGH JOB. THANKS THANKS FOR YOUR HELP.

by in Waterloo, AL on July 23, 2013
3 answers 2 comments
ANSWER by on July 24, 2013
check for a vaccum leak at throttle body and intake manifold
ANSWER by on July 24, 2013
YES CK FOR VAC LEAK AND POSS RUN A CAN OF SEAFOAM THRU T/B SO YOU ARE SURE ITS CLEAN
ANSWER by on July 27, 2013
Have you replaced the thermostat at some point? Does the temperature always get to normal? Does the bad idle issue happen hot/cold?
COMMENT by on July 27, 2013
I DID REPLACE THE THERMOSTAT,BUT IT MAY NOT BE TO SPEC. IT IS A 160 DEGREE THERMOSTAT. I DON'T REALLY KNOW WHAT IT IS SUPPOSED TO BE. MAYBE A 180. THE TEMP ALWAYS GOES TO ABOUT 160. I DID CHECK THE TEMP SENSOR AND IT IS WORKING. I CAN UNPLUG AND PLUG IT BACK AND IT CHANGES THE IDLE A LITTLE. THANKS FOR INPUT. AND YES, IT DOES IDLE A LITTLE DIFFERENTLY COLD AS TO WHEN IT IS HOT.
COMMENT by on July 27, 2013
You should put at least a 185 T-Stat back in it. It should have come stock with a 192. Those early computer systems are very temp sensitive. If it is running cold, it will have trouble going into closed loop (full computer fuel control) operation. That may be some (if not all) of your problems. Unless you live in a real hot climate or the car is modified, keep the T-Stat stock temp.