Rough idle ?

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Jun 14, 2010 | 09:10 PM

romanstryker1

Thread Starter

3rd Gear

Joined: Jun 2010

Posts: 3

Likes: 0

From: Stryker Oklahoma

Rough idle ?

Hello, First off im glad I found this site it looks good , So I recently purchased a 1994 LT-1 Vette, Auto trans with 109,000 miles , The work that has been done to it before me so far, New MSD Opti, New ICM, New IAC, New Taylor wires, New MSD coil, And New E3 Spark Plugs, & EVAP Cannister & New Fuel pump . Also all of the pigtails for the above parts are New , The guy had all the reciepts for the parts. So heres whats going on when I start the car when its cold , it idles rough but when it warms up theirs no problems it idles fine ,once though when I came to a stop after coming off the highway it idled rough so I put it in Park and reved it a couple of times and it was fine. I pulled codes due to a check engine light that keeps flashing on and off and it showed a code 42. Ive checked all of the wiring and had the PCM tested and both were good , all Vac hoses look good as well, so im now lost and not sure where to troubleshoot next ?? Thanks for any advice .

Jun 14, 2010 | 09:29 PM

Harsh20

Instructor

Joined: Nov 2008

Posts: 199

Likes: 1

From: Asheboro NC

one thing you will want to do is clean your throttle body.

Jun 14, 2010 | 09:49 PM

cfi

Instructor

Joined: Aug 2007

Posts: 107

Likes: 0

From: Lansdale PA

Code 42 relates to the Ignition Control Module. Could be just a ground but they do go bad because of heat. Not too expensive and you can do it yourself

Jun 14, 2010 | 10:03 PM

Seattle C4

Racer

Joined: Apr 2008

Posts: 447

Likes: 0

From: Woodinville WA

$1.49 Can of Gum Out!!! Still one of the best starting points. And give it a good cleaning too! You may want to get the MAF cleaner those get clogged as well.

Jun 16, 2010 | 07:21 PM

romanstryker1

Thread Starter

3rd Gear

Joined: Jun 2010

Posts: 3

Likes: 0

From: Stryker Oklahoma

Quote:

Originally Posted by cfi

Code 42 relates to the Ignition Control Module. Could be just a ground but they do go bad because of heat. Not too expensive and you can do it yourself

Thanks for the info, I have tried to locate the ground for the ICM but no luck . I need to buy the F.S.M. for this car. Do you have any idea where the ground is for the ICM on the 94 ?? Thanks.

Jun 16, 2010 | 08:44 PM

cfi

Instructor

Joined: Aug 2007

Posts: 107

Likes: 0

From: Lansdale PA

A FSM is a good idea. It will have a testing sequence to track down connectivity problems. I don't have mine copied to e-mail it to you. Hopefully agent 86 will read this he has pdf's. of everything.

Jun 17, 2010 | 08:35 AM

runner140*

Le Mans Master

Joined: Mar 2004

Posts: 8,700

Likes: 298

From: Ft. Lauderdale Fl

Clean your throttle body....completely. Take it off, clean all the passages, clean or replace the idle motor (its cheap), clean the butterflys and replace with a new gasket.

Check for a vacuum leak.

Get back to us.

Last edited by runner140*; Jun 17, 2010 at 08:35 AM. Reason: add

Jun 17, 2010 | 08:50 AM

jispr

Instructor

Joined: Sep 2004

Posts: 208

Likes: 1

From: Lawrenceville GA

Recently I removed the TB took i apart and let it soak in parts cleaner.
reassembled with new gasket set and the resulting idle was 100%
improved!!! Course I did change the tpi and iac.