missfire at idle
Thread Starter
Intermediate
Joined: Apr 2013
Posts: 32
Likes: 0
From: chesapeake Virginia
missfire at idle
hello my 98 corvette A4 coupe with 106,900 miles will shake a little bit at idle and the tach will vary about a hundred RPM up and down at random you can hear and fell a miss from the tailpipe no codes and when I bought the car 2 months ago I put new NGK iridium plugs gapped to about .040,Delphi wires,ACdelco fuel filter,cleaned the MAF with CRC MAF cleaner and fresh gas helped it but its still there when I first got it the rpms would vary when crusing at a stable speed now it wont do that but still at idle and when shutting down the car shakes like its trying to diesel for maybe 2 seconds when shut off its like a gradual slowdown.with the AC on both the run on and unstable idle are reduced but not completely gone
thanks for any help
thanks for any help
Drifting
Joined: Oct 2002
Posts: 1,335
Likes: 76
From: Bedford Va.
I see you had the car for 2 months
is the car stock? Are there signs of previous mods?
It's not unusual for a little rock and roll and when you turn these cars off the torque tube makes a little noise/rattle.
Under heavy load do you have any misfires?
is the car stock? Are there signs of previous mods?
It's not unusual for a little rock and roll and when you turn these cars off the torque tube makes a little noise/rattle.
Under heavy load do you have any misfires?
Thread Starter
Intermediate
Joined: Apr 2013
Posts: 32
Likes: 0
From: chesapeake Virginia
no not under a heavy load anything over idle I don't feel anything abnormal I accelerates fine but now the balancer is walking so I seem to have a bigger problem to worry about at the moment also no codes no p0300 or p030X no codes at all
Thread Starter
Intermediate
Joined: Apr 2013
Posts: 32
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From: chesapeake Virginia
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Vacuum leaks or air leak in the ducting between the MAF and Throttle body. Easy to check.
Check the PCV tubing, fittings abd rubber hoses. They can deteriorate and crack. Most of it is behind the intake manifold.
Bill
Check the PCV tubing, fittings abd rubber hoses. They can deteriorate and crack. Most of it is behind the intake manifold.
Bill
Thread Starter
Intermediate
Joined: Apr 2013
Posts: 32
Likes: 0
From: chesapeake Virginia
also ive seen you on some of the balancer threads I got a powerbond balancer do you have any suggestions for the install im gonna try to find a big enough strap wrench to hold the balancer
thanks
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Tech Contributor
Joined: Dec 1999
Posts: 32,910
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
You could have dirty or damaged injectors. Try running some chevron techron in a couple tanks of fuel.
Use a mechanics stethoscope and listen to each injector fire. They all should sound the same when they fire. If you have one that weak or dirty, it can sound different.
Check out these U tube vids:
Use a mechanics stethoscope and listen to each injector fire. They all should sound the same when they fire. If you have one that weak or dirty, it can sound different.
Check out these U tube vids:
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
did you do a manifold vacuum test before you bought the car? takes about 30 seconds and will let you know if there is something out of wack with compression since the gauge will flutter
that's the very first test i would do. it takes under a minute and can quickly rule in or rule out the most serious problems
that's the very first test i would do. it takes under a minute and can quickly rule in or rule out the most serious problems
Drifting
Joined: Sep 2009
Posts: 1,719
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From: cinnaminson n.j.
St. Jude Donor '14
If he's got a leak at 1 or 2 intake seals at the head, that's a different story.
Thread Starter
Intermediate
Joined: Apr 2013
Posts: 32
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From: chesapeake Virginia
[QUOTE=Bill Curlee;1587187031]You can try the Idle relearn. It wont hurt.. It does it on its own over time. Try sears for the strap wrench[/QUOTE
i wanted to ask if i still have to drop the cradle down a bit to just move the rack out of the way?and what temp. should i heat the balancer to put it on?
thanks
i wanted to ask if i still have to drop the cradle down a bit to just move the rack out of the way?and what temp. should i heat the balancer to put it on?
thanks
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Some cars you can just get the rack out without moving the K member. I can slide mine out.
HEAT,, About 180 to 200 deg Doesnt need to be much. Just heat the HUB
HEAT,, About 180 to 200 deg Doesnt need to be much. Just heat the HUB
Thread Starter
Intermediate
Joined: Apr 2013
Posts: 32
Likes: 0
From: chesapeake Virginia
thanks for the help
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
YES,,, The center part of the dampener. Just use heavy duty heat gun or a propane torch. Once its heated, it will go on a LOT easier.
No need to heat the entire dampener.
I also put some engine oil on the inside and outside. MAKE SURE that you put some on the outside of the hub and some on the cover seal lip!