idle speed too high
Thread Starter
Safety Car
Joined: Jul 2002
Posts: 4,548
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From: SCMR Rat Pack'r Charter Member, Inland Empire Chapter
idle speed too high
Its a '91 L98 coupe, ZF6 manual trannie, 108k miles and the idle speed is a constant 1000 rpm. It doesnt drop down to 500-700 rpm which I understand to be normal after its warmed up. If I turn the AC on it goes up another 100 rpm and the IAC is less than a year old. Same for the oxygen sensor, Plugs, wires, dist cap and rotor. I know I have 1 fuel injector thats marginal but all else is ok as far as I know. Any ideas?
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: idle speed too high (DarkHalo)
If you didn't clean the IAC pintel bore under the TB last year, do so now and reset the base idle.
Also, clean the TB plates and bores with some TB cleaner.
If it still idles high, look for a vacuum leak.
Also, clean the TB plates and bores with some TB cleaner.
If it still idles high, look for a vacuum leak.
Thread Starter
Safety Car
Joined: Jul 2002
Posts: 4,548
Likes: 3
From: SCMR Rat Pack'r Charter Member, Inland Empire Chapter
Re: idle speed too high (65Z01)
How do you reset the base idle? I dont find that in my Haynes manual. By the way, thanks for the info. Ill make a run to Pep Boys for some throttle body cleaner and try that immediately. :cheers:
and no, I didnt clean the IAC bore out when I replaced it. :cry I just slapped the new one in and it did fix the problem with the idle not increasing when the AC was turned on.
[Modified by DarkHalo, 1:56 PM 11/1/2003]
and no, I didnt clean the IAC bore out when I replaced it. :cry I just slapped the new one in and it did fix the problem with the idle not increasing when the AC was turned on.
[Modified by DarkHalo, 1:56 PM 11/1/2003]
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: idle speed too high (DarkHalo)
Base idle setting procedure is on my site, see sig. below.
I bet cleaning the bore will cure the problem as they get pretty dirty. Q-tips work well so long as you check with a mirror & light to assure no threads get stuck in there.
I bet cleaning the bore will cure the problem as they get pretty dirty. Q-tips work well so long as you check with a mirror & light to assure no threads get stuck in there.
Thread Starter
Safety Car
Joined: Jul 2002
Posts: 4,548
Likes: 3
From: SCMR Rat Pack'r Charter Member, Inland Empire Chapter
Re: idle speed too high (65Z01)
Good site with some good service info! I cleaned out the IAC bore, it was a bit grubby, then reset the IAC pintle position by shorting pins A and B in the ALDL connector, turning the key on, letting it extend the pintle, turn the key off and pull the IAC connector. Pull the ECM fuse, turn the key on, tturn it off then start the engine. The idle stayed a min of 1000 RPM but now it tends to hover at closer to 1200 RPM when I let off the throttle. I blip the gas a couple times and it drops to 1000 RPM. But no lower. Well shoot....maybe Ill try resetting everything again in the morning. :(
Melting Slicks
Joined: Apr 2002
Posts: 2,118
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From: St. Charles, MO Route 66 Corvette Club
Re: idle speed too high (DarkHalo)
The procedure mentioned is not exactly what is printed in my 89 Helms GM manual for base idle adjustment. I have used the GM procedure on my car and it produces good results....on my 89. If you want a summary of this, please send me an email. Regards, Sam
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Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
Re: idle speed too high (DarkHalo)
Ah ha, you need to open the IAC connecor BEFORE you turn the key off.
Anyway, once you cleaned the IAC bore & TB you need to reset base idle with the pintel fully extended. So after you open the IAC connector,remove the ALDL jumper wire and start the engine. Then back off the TB set screw to set base idle to 450 RPM.
Anyway, once you cleaned the IAC bore & TB you need to reset base idle with the pintel fully extended. So after you open the IAC connector,remove the ALDL jumper wire and start the engine. Then back off the TB set screw to set base idle to 450 RPM.