Rough Idle Advice..

Reply Subscribe

Thread Tools

Search this Thread

Sep 2, 2018 | 08:55 PM

LoveMyVette08

Thread Starter

Cruising

Joined: Sep 2018

Posts: 10

Likes: 1

Rough Idle Advice..

My 2008 base A-6 Vette now with 130K miles on it, still runs like new, awesome acceleration, great fuel economy and overall peak performance.. truly still like a new car. All is perfect except when idling.. it's rough, randomly misses and when I look under the hood I can see the engine intermittently shaking. I tried troubleshooting basic items and later replacing sparkplugs and wirings, but with no success. Also, I have no fault codes or check engine light warnings what so ever.

Is this a common issue on older Vettes or could I maybe have something like a hard to diagnose vacuum leak somewhere? I haven't taken the car to any shop yet because since this is an idle only issue and otherwise the car's performance is as good as always, it's kind'a more bothersome than a major problem I feel needs an emergency fix.

I bought the car new and haven't had a single major issue with it aside from minor things and regular maintenance.. really an awesome car, love it!

Thanks a lot in advance for any advice on what I should be on the lookout for or trying to troubleshoot

Last edited by LoveMyVette08; Sep 2, 2018 at 08:56 PM.

Sep 11, 2018 | 04:06 PM

thedperrys

Intermediate

Joined: Apr 2015

Posts: 38

Likes: 21

From: Lake Lanier, Georgia

Going after the simple stuff first, I would suspect a dirty fuel injector. Give her a dose of Techron Complete Fuel System Cleaner.

Sep 11, 2018 | 09:59 PM

Dano523

Race Director

Joined: Dec 2013

Posts: 12,502

Likes: 3,629

Quote:

Originally Posted by thedperrys

Going after the simple stuff first, I would suspect a dirty fuel injector. Give her a dose of Techron Complete Fuel System Cleaner.

Also, at 100K, really need to replace the spark plug wires (don't forget the dielectric grease), make sure to clean the coil connectors and sockets (little dielectric grease here as well), clean the MAF, and replace the air filter as well. Next, give the intake hoses a quick check for cracks/leaks, including pulling the check valve at the brake booster to give it a touch of dielectric grease on the rubber grommet to solve any light leak there too.

Short of basics above, do a quick data log on the car to check for a lazy O2 sensor that may need too be replaced as well.

Last edited by Dano523; Sep 11, 2018 at 10:00 PM.

Sep 12, 2018 | 05:15 AM

LoveMyVette08

Thread Starter

Cruising

Joined: Sep 2018

Posts: 10

Likes: 1

Thanks for the reply.. will follow your advice! So far the basics that I've done while the problem remains the same:

- No fault codes
- Filters replaced
- Throttle body out and cleaned
- CO2 sensor replaced
- New sparkplugs
- New injectors
- New wirings

Will keep looking, thanks again

Last edited by LoveMyVette08; Sep 12, 2018 at 05:18 AM.

Sep 12, 2018 | 11:24 AM

taguid

Instructor

Joined: Nov 2017

Posts: 135

Likes: 42

From: Gonzales LA

Also, I have read that you should move the wire to the back of the alternator away from the nearby plug wire because it can cause misfires.

Sep 12, 2018 | 02:07 PM

LoveMyVette08

Thread Starter

Cruising

Joined: Sep 2018

Posts: 10

Likes: 1

Quote:

Originally Posted by taguid

Also, I have read that you should move the wire to the back of the alternator away from the nearby plug wire because it can cause misfires.

Hey taguid, I didn't know about that one but makes sense and will check it for sure!!! Thanks a lot for the tip!

Last edited by LoveMyVette08; Sep 12, 2018 at 02:07 PM.

Oct 4, 2018 | 01:19 PM

719c6

Instructor

Joined: Jul 2014

Posts: 212

Likes: 42

From: Mid MO

Quote:

Originally Posted by LoveMyVette08

Hey taguid, I didn't know about that one but makes sense and will check it for sure!!! Thanks a lot for the tip!

Updates? Did you find out the reason for the rough idle?

Oct 4, 2018 | 01:55 PM

LoveMyVette08

Thread Starter

Cruising

Joined: Sep 2018

Posts: 10

Likes: 1

Quote:

Originally Posted by 719c6

Updates? Did you find out the reason for the rough idle?

Hi, thanks a lot for your interest!

I did not yet found the problem and the issue is a bit worse. The rough Idle has now expanded to continuing misses across the RPM range. Cold less, warm more. I have an appointment for next week with a private mechanic to do a compression test and check if there are any possible issues with the valves. I have no idea where else to look by myself. Power is still great and fuel economy seemingly unchanged but the continued rough operation and misses worries me that I might get eventually stranded one of these days. Let's see what the mechanic comes up with. I did a full diagnostics scan last week and once again, no fault codes..

Last edited by LoveMyVette08; Oct 4, 2018 at 01:58 PM.