I have a miss and need help
Thread Starter
Instructor
Joined: Jun 2005
Posts: 219
Likes: 0
From: Davison Michigan
I have a miss and need help
Well my L98 has a miss. Ran fine last fall when I put it away. I did some work on it over the winter and now it has a constant miss at idle. I have not had it out on the road yet.
Don't know if I caused it but here is a list of things I did over the winter.
Changed plugs wires and rotor.
Changed fuel filter
Removed exhaust and exhaust manifold. Ported and replaced manifold and pre-cats
I checked all the plug wire fits to plugs and cap.
I put a timing light on each wire and all fire the timing light.
Any suggestions? How can I determine which cylinder is the problem?
Thanks
Don't know if I caused it but here is a list of things I did over the winter.
Changed plugs wires and rotor.
Changed fuel filter
Removed exhaust and exhaust manifold. Ported and replaced manifold and pre-cats
I checked all the plug wire fits to plugs and cap.
I put a timing light on each wire and all fire the timing light.
Any suggestions? How can I determine which cylinder is the problem?
Thanks
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
If it's a CONSTANT miss at idle...... and it does it EVERY tiem you crank it up........
Let the engine cool completely.....................
Open the hood and leave it open.
Crank it up for about 30 SECONDS. Don't 'rev' it up, just let it idle.
Turn it off and jump out quickly.
Lick your finger and place it on the exhaust header pipe just where it attaches to the head. It's NOT going to be hot enough to burn you so don't worry about that.
You'll be able to EASILY feel the dead cylinder(s).
Whichever ones aren't hot, are the dead one(s).
Let the engine cool completely.....................
Open the hood and leave it open.
Crank it up for about 30 SECONDS. Don't 'rev' it up, just let it idle.
Turn it off and jump out quickly.
Lick your finger and place it on the exhaust header pipe just where it attaches to the head. It's NOT going to be hot enough to burn you so don't worry about that.
You'll be able to EASILY feel the dead cylinder(s).
Whichever ones aren't hot, are the dead one(s).
Thread Starter
Instructor
Joined: Jun 2005
Posts: 219
Likes: 0
From: Davison Michigan
Your not called vett NUT for nothin are you. Just kidding. Sounds like a good suggestion but I think I might try an infared temp gun. I don't have the guts to use my finger.
And I will buy some seafoam tomorrow.
And I will buy some seafoam tomorrow.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
At night when it is dark, disable the hood lights and start the engine and look for sparks along each plug wire. Replace broken wire looms and dress the plug wires so they do not touch anything at ground potential. Measure each plug wire with an ohmeter. They should measure about 5000 ohms per foot.
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
Have you checked for any stored codes in the ECM? This should be your first step to confirm the ECM has not picked up a problem with the engine control system. You can get a free ECM code key at Auto Zone just for asking and it looks like this:
Hope this info is helpful to you.
Hope this info is helpful to you.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
When Vic'89 and I were discussing my possible bad injector problem he suggested I spray a little water onto each exhaust header pipe in search of a dead cylinder. But I had lost 30-40chp so it sounded like maybe a completely dead injector.
Since your issue is a miss all cylinders may be getting enough fuel to partially fire. Though you might try the water spray or wet finger test anyway.
I think the deal with the fniger tip is to rewet the finger after touching a header pipe...
And you would not run the engine long enough to really heat the header tubes to a dangerous temp.
Since your issue is a miss all cylinders may be getting enough fuel to partially fire. Though you might try the water spray or wet finger test anyway.
I think the deal with the fniger tip is to rewet the finger after touching a header pipe...
And you would not run the engine long enough to really heat the header tubes to a dangerous temp.
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Thread Starter
Instructor
Joined: Jun 2005
Posts: 219
Likes: 0
From: Davison Michigan
Well I am kind of embarassed to tell you what I found. But I figure I owe you the answer, just for closure, if you know what I mean. So as it turned out, I decided that before I burned my fingers i would just double check to make sure the plug wiring was correct. And I found I had #3 and #4 switch at the cap. Now everything is running fine. Just got to get the exhaust hooked at a muffler shop.
Thanks for the help.
Thanks for the help.
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
I LOVE it when I find the problem is something I screwed up.
But I HATE it too and it's so PAINFUL trying to get my leg contorted enough to kick my own butt.
Glad you got'er straightened out.
But I HATE it too and it's so PAINFUL trying to get my leg contorted enough to kick my own butt.
Glad you got'er straightened out.