High idle
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
High idle
My 1990's idle is probably 1800. I am guessing a little since the tach doesn't work. I have looked all over for vac leaks but not found any. What else could it be?
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Tape off throttle body. Idles there is a vacuum leak. Stalls check for codes. IAC not extending would cause condition. Misadjusted cruise control cable.
Last edited by Kevova; Apr 16, 2018 at 08:53 AM.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
Likes: 508
From: South-central Missouri
But, generally, starting with removing the air duct and (using a book or flat surface of some kind) to close off the air intake completely while the engine is running is how one determines if there is an air (aka "vacuum") leak somewhere.
If the engine continues to run, then start eliminating mechanicals (e.g., throttle body sticking or IAC not responding, cable linkage, return spring tension, etc.) and gaskets/fastener torque.
Last edited by Paul Workman; Apr 16, 2018 at 09:29 AM.
Intermediate
Joined: Jul 2014
Posts: 32
Likes: 3
From: State College Pennsylvania
Idling Issue
This must be a common problem with the 1990's model years, because it is even referenced in my 1994 owner's manual with a quick fix remedy. I own a 1994 automatic LT1, and have had in the past a fast idle and engine surging issue also. I was so concerned that when I was stopped at a red light, I would put my car in neutral if the engine started surging in case I bumped into the car ahead of me. Not sure what page this remedy is on your manual, but for my 94, it is located on page 46 under the title 'Rough Idling'. The manual provides the following solution to remedy this situation. "1. Set the parking brake. 2. Shift an automatic to "P" (Park) or manual transmission to "N" (Neutral). 3. Press the accelerator until your tachometer reads 2,000 rpm and hold for two minutes. Hope this helps, it worked for me. 
