Irregular Idle ...like some ghost is accelerating !!!
Thread Starter
Le Mans Master
Joined: May 2007
Posts: 8,448
Likes: 27
From: Valparaiso
Irregular Idle ...like some ghost is accelerating !!!
Hi !!
I got an 87 VETTE Chromed intake...not sure which version of the engine is but there is a notorius problem,the idling is so irregular
its like some ghost its accelerating ...it goes up and down
what could be the cause of this problem ?
thanx !!!
I got an 87 VETTE Chromed intake...not sure which version of the engine is but there is a notorius problem,the idling is so irregular
its like some ghost its accelerating ...it goes up and down
what could be the cause of this problem ?
thanx !!!
Safety Car
Joined: Jul 2007
Posts: 3,918
Likes: 1
St. Jude Donor '09-'10-'11-'12-'13-'14-'15-'16
Hi- Check to see if your throttle position switch is loose and slightly moving around! If it's not, I'll be back later or somebody else will take you from there. It's the very first place I'd look with what you've described. 
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
Check the TPS, it should be set at .54 volts with the key turned on only. Next check for vaccum leaks (check all hoses).
Last, I would pull the throttle body and carefully clean it with carb cleaner and a brush. I would take off the Idle Adjustment Control first (on right side of TB with 4 wire plug) before cleaning. This often goes bad and can be replaced easily. Be sure that the new (or if the old one looks good) that the pintal is not more than 1-1/8" from the base under the gasket to the end of the pintal. New IAC is about 45-55 depending where you buy it.
Last, I would pull the throttle body and carefully clean it with carb cleaner and a brush. I would take off the Idle Adjustment Control first (on right side of TB with 4 wire plug) before cleaning. This often goes bad and can be replaced easily. Be sure that the new (or if the old one looks good) that the pintal is not more than 1-1/8" from the base under the gasket to the end of the pintal. New IAC is about 45-55 depending where you buy it.
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
Yeah, check voltage at TPS with voltmeter. Upper two wires with key on or motor running.
Check for any vacuum leaks under the hood too. You can usually hear them hissing.
Also, remove your IAC valve (idle air control) located under the throttle body and clean it good with a mild wire brush. Then do a complete reset of the idle speed.
Here's how:
https://www.corvetteforum.com/techti...D=55&TopicID=2
Note: The tech tip leaves out the fact that you need to unplug EST when doing this. Here's a pic of the EST.
If you just got this car and plan to do any work on it yourself, I highly encourage you to buy the original GM shop manual for your car. Also called Helms or FSM.
Check for any vacuum leaks under the hood too. You can usually hear them hissing.
Also, remove your IAC valve (idle air control) located under the throttle body and clean it good with a mild wire brush. Then do a complete reset of the idle speed.
Here's how:
https://www.corvetteforum.com/techti...D=55&TopicID=2
Note: The tech tip leaves out the fact that you need to unplug EST when doing this. Here's a pic of the EST.
If you just got this car and plan to do any work on it yourself, I highly encourage you to buy the original GM shop manual for your car. Also called Helms or FSM.
Thread Starter
Le Mans Master
Joined: May 2007
Posts: 8,448
Likes: 27
From: Valparaiso
thanx for your info !
i will buy those books soon
as well as the chilton
i have 10 years of experience working on my 82 Firebird S/E and another 89 Formula 350 and the Vette shares a lot with the F-Bodies
So,as a vette newbie im not a beginner
but,i forgot a lot of things,a lot of time since i have done any under the hood work,but with my new vette,its hood time !!!
thanx guys !
i will buy those books soon
as well as the chilton
i have 10 years of experience working on my 82 Firebird S/E and another 89 Formula 350 and the Vette shares a lot with the F-Bodies
So,as a vette newbie im not a beginner
but,i forgot a lot of things,a lot of time since i have done any under the hood work,but with my new vette,its hood time !!!
thanx guys !
Race Director
Joined: Apr 2004
Posts: 17,066
Likes: 3
From: Milpitas ca
Yeah, check voltage at TPS with voltmeter. Upper two wires with key on or motor running.
Check for any vacuum leaks under the hood too. You can usually hear them hissing.
Also, remove your IAC valve (idle air control) located under the throttle body and clean it good with a mild wire brush. Then do a complete reset of the idle speed.
Here's how:
https://www.corvetteforum.com/techti...D=55&TopicID=2
Note: The tech tip leaves out the fact that you need to unplug EST when doing this. Here's a pic of the EST.
If you just got this car and plan to do any work on it yourself, I highly encourage you to buy the original GM shop manual for your car. Also called Helms or FSM.
Check for any vacuum leaks under the hood too. You can usually hear them hissing.
Also, remove your IAC valve (idle air control) located under the throttle body and clean it good with a mild wire brush. Then do a complete reset of the idle speed.
Here's how:
https://www.corvetteforum.com/techti...D=55&TopicID=2
Note: The tech tip leaves out the fact that you need to unplug EST when doing this. Here's a pic of the EST.
If you just got this car and plan to do any work on it yourself, I highly encourage you to buy the original GM shop manual for your car. Also called Helms or FSM.
Team Owner
Joined: Oct 2004
Posts: 35,065
Likes: 0
From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
I just had the same problem It would go from 600 to 1200 RPMs and back down and up again. Especially happened when the engine was warm. When I raced the motor it wouldn't settle back into idle.
It was my injectors. Injectors are easy enough to check. See if you have 16-18 Ohms resistance on each. Anything under 12 is considered shot.
It was my injectors. Injectors are easy enough to check. See if you have 16-18 Ohms resistance on each. Anything under 12 is considered shot.
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