dontruitt

I have a 1987 stock 'vette with 123,000 miles on it. The day before we left for Carlisle, the engine started to hold a high idle when I stopped at lights etc. Prior to this there were no problems with the idle dropping to @600 RPM in drive while stopped. Now it stays 900 - 1000 when I stop and goes to 1400-1500 if I shift into neutral. I can get it to drop by "bliping" the gas pedal. I have sprayed the throttle body plates and interior throttle body from the front with cleaner as instructed on the can (STP) but didn't change anything.

Any help will be appreciated. Thanks in advance for your help

Midnight 85

With that many miles on it I would bet you have worn a throttle shaft bore in the throttle body. Grab hold of the linkage and see if you can move it back & forth. What is happening is it is slightly hanging up because of the slop in the shaft bore. Blipping the throttle knocks it loose.

dontruitt

Nope, the linkage hardly moves in or out. So that apparently is not the primary problem.

383vett

Is the cable binding somewhere? Something is happening when you blip the throttle that is allowing the throttle blades to close from a previously open position

0Paul Ruggeri

Disconnect all the cables from the throttle and try it.

SurfnSun

Id also check for a vacuum leak.

dontruitt

I have company coming now so I will try those things as soon as I get a chance and let you know the results. Thanks for the suggestions. BTW, where would I have a vacuum leak that blipping the throttle would take care of ????

SurfnSun

I know it sounds weird but my car was exhibiting high idle as well and I could sometimes blip the throttle and it would settledown. I would also get some idle hunting as well.

Turned out to the 90 degree angle vacuum fitting underneith the injector cover on the driver's side.

RVY

Look for a slight cable bind where the cable is fastened to the throttle linkage. Been there.

Randy93

Qiken

JrRifleCoach

IAC

Will fail without warning.

dontruitt

Thanks, I'll check those areas out.

Road Agent

I am presently troubleshooting the same problem! I will let you know what I come up with.

cherokeeL98

i have same problem on my 89. Changed iac off the bat nothing changed. Can a bad oxy sensor make it idle high? Is the tps next to replace if no vaccum leaks?

JrRifleCoach

Is the idle problem during open or closed loop?

cherokeeL98

its still plugged in and i noticed some mpg loss. Just recently idles high. Yesterday i was driving and it just died out of no where. Drove 100miles and it ran fine and idled high. Then it idled fine the next day then today its idles high no matter what.

jeffp1167

when it does it open hood and you will see the linkage is slightly away from the idle stop screw. push the linkage against the idle stop screw and I bet it idles down.

time for a rebuilt throttle body or add a extra spring to get it to close. Is what causes it. The throttle blades over time wear into the bores and hang up a bit and the return spring gets weak over time. It's that quik snap of the accelerator that forces the blades shut.

cherokeeL98

its not that it sets on the screw everytime. The previous owner has two springs on there to help pull back. I have a 1/4inch of threads sticking out the back on the idle screw is that too much? I unplugged sensors, replaced dry rotted vac caps made sure lines were tight. Replaced iac as mentioned before. Unplugged oxy sensor no diff. What is next? I can just back the screw out and drive i guess.

Tripleblack90

Just went through this... I changed the ECM and reset the base idle. I replaced everything.......Trust me on this. This is your problem. The added springs are not necessary.