Looking for someone that can help me with an idle problem with my 88 vette.my idle stays between 1100-1200 rpm i have tried everything,sometimes it does goes down to 650-700 rpm but very rarely and when i turn the engine off and restart it goes back for this reason i dont think it is a vacuem problem even though i have checked for leaks.when i go thru the adjust idle procedure in this website when i ground a&b terminals and then disconnect the iac instead of the idle coming down it will either stay the same or go up to about 1400-1500rpm i have listed is what i have done.
replaced iac
cleaned tb
removed injectors and had them sent to Rich for cleaning
new upper intake,tb, and runner gaskets
replaced temperture sensor
checked for vacume leaks
switched out maf sensor with known good unit
anyones help would be greatly appreciated becouse i am very frustraded also mybe someone can explain something to me . i removed the iac from the tb when igrounded a&b terminals and turned the ignition on should'nt the iac move,well it did not.if that is the case would i have a bad ecm or chip .the chip is an ads which i got with the car so i do not have the stock one.that is the only non-stock item on the car.

mybe someone can explain something to me . i removed the iac from the tb when igrounded a&b terminals and turned the ignition on should'nt the iac move,well it did not.if that is the case would i have a bad ecm or chip .the chip is an ads which i got with the car so i do not have the stock one.that is the only non-stock item on the car.

 

i'll take a stab at this. im gonna go out on a limb and say your iac didn't extend when you went thru the procedure because it was already fully extended(trying to shut off the massive amount of air your getting in the intake at idle). from what you stated you went thru the idle adjustment procedure correctly, but you made no mention of adjusting the throttle blades? if you closed the blades and you are still idling at this speed with the iac closed , you have a very bad vacuum/ intake leak somewhere. check your throttle bushings first. go to your local parts store & get a cheapie propane torch. put a rubber hose on the end of the torch & run the engine. turn the propane on & place the hose end at various suspected leak points. the engine will rev up when you get close. also , do your power brakes seem to function properly? a busted diaphragmn there can also cause the problem.
hope this helps .

 

i almost forget. check & adjust your tps voltage.

 

i have adjusted tp voltage,used two different TB 3 fifferent IACs.the reason that i say that my IAC is not moving is that i have removed the iac from the tb and watched the iac during key on engine off and field test modes and no movement,as far as i know the iac should return to it normal position when the engine is not running and then move again when key is turned on.

 

Hey Mac567

I have the EXACTLY the same problem with my 87 vette.
Have tried everything too but nothing helped.
2day I got it down to 750 rpm for the first time for a few minutes... I adjusted the ignition timing to 6 degrees, (was 8). (I did remove the brown /black cabel first) Now, when I got back after the test drive I turned the engine off and then on again, guess what? Same old high idle, BUT the ignition timing was VERY early now (off the scale BUT the car ran fine, no misfiering!!?) and when I tried to reset it to 6 degree the engine died even before I got the marking back on the sawtothed scale... is this sick or what?

Have u pulled the codes on your 88? I am about to in a few weeks to see if that might give an indication of some other error.... could be the ECM?

Let me know if u get ur idle down!!
Tony@rem.zzn.com
Good luck
/Tony