speratic miss at idle
Thread Starter
Racer
Joined: May 2014
Posts: 416
Likes: 29
From: diamond bar ca
speratic miss at idle
Hi folks, I have a 96 a4 lt1 which has a slight miss at idle, car runs fine pulls good and runs fine at steady speed, but when idling at light or any time it sometime will idle good and others time you can feel a slight miss , when ac is on it seems to make it worse, or if it is in neutral it will idle smoother when I put it in drive. also when I blow it out on the freeway and then come to a stop it idles smooth, and after while it will start up again,, im confused, could it be a vacuum leak, bad plugs, or what,,, hope u can help... thanks
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
I will assume that there are no error codes. My inclination would be to change the plugs. They recommend changing plugs at about 100,000. If your close or over...plugs are cheap. Go with standard AC Delco.
4th Gear
Joined: Jun 2015
Posts: 4
Likes: 0
Changing the fuel filter solved that exact problem on my 96. From how it looked i suspect it was still the original one that had been on for 19 years. The nice thing is that it's a cheap part to try. The TB cleaning and plugs as suggested are also cheap and easy maintenance that will do the car good in any case
Thread Starter
Racer
Joined: May 2014
Posts: 416
Likes: 29
From: diamond bar ca
Thanks for the tips,,, plugs have been replace with in the last10k miles TB has been cleaned wires have been relaced, a friend of mine is adamate the the gas hear in so cal is the problem. Sooo i will replace the plugs since they were in the car when i got it just as a precaution and will let ya know,,,,
Race Director
Joined: Oct 2011
Posts: 16,087
Likes: 819
From: Dallas Texas
2025 C4 of the Year Finalist - Modified
kimmer, I know your car is a 92. 92 and 93 C4 LT1 are batch fire. From what I read, they won't idle as smooth as the 94-96. With that said, I changed my fuel injectors a while back(2 were leaking), and my idle improved a good bit.
Le Mans Master
Joined: Jul 2009
Posts: 6,381
Likes: 66
From: SF bay area C.A.
C4 of the Year Finalist
That's the one thing I have not done , could probably use a new set. Kind of gotten use to it sounding like it has a cam.
Last edited by kimmer; Jul 16, 2015 at 11:58 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
I had an aftermarket ZZ9 cam from TPIS, Chaska Minn....Marvin Cotrell, it went into my L98 block and lasted about a year, until that symptom showed up, intermittent bad idle, it drove me krazy for years on end, tried everything from cyl heads UP, changed induction, changed all sorts of crap.....but some years ago when gas hit 4 bux I inquired on the net about a stock L98 cam and a friend sent me one from a Camaro.....
when tearing out that POS ZZ9 cam, the 6 of the lobes were all funky looking on the surface, like the cam finish was destroyed.....I pulled the lifters outta their order on the bench one at a time, and examined them closely, no defects noted....under a mag glass and bright light....
so I wanted better MPG, and so it's the same, but the intermittent idle problem went away for some 6 years now.....
it's the CAM, especially any hotrod cam, and for sure if it's the above POS.....
when tearing out that POS ZZ9 cam, the 6 of the lobes were all funky looking on the surface, like the cam finish was destroyed.....I pulled the lifters outta their order on the bench one at a time, and examined them closely, no defects noted....under a mag glass and bright light....
so I wanted better MPG, and so it's the same, but the intermittent idle problem went away for some 6 years now.....
it's the CAM, especially any hotrod cam, and for sure if it's the above POS.....