Misfires....
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Misfires....
What might be causing this. Multiple misfires on Cly #1 & #2.
I have checked both ends of the wires and they appear to be tight. All other cylinders have 0 misfires during this scan. The plugs are new. Carbon tracking maybe? I have had a code on the low resolution signal recently. I cleared it and it has not returned.
I have checked both ends of the wires and they appear to be tight. All other cylinders have 0 misfires during this scan. The plugs are new. Carbon tracking maybe? I have had a code on the low resolution signal recently. I cleared it and it has not returned.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Always include the year vette you are asking help for! At night in the dark, turn off the underhood lights and engine idling, look for sparks along each plug wire. Replace missing or broken wire looms, dress the plug wires so they do not touch metal. Plug wires have microscopic pinholes in them and can spark through these holes to metal. Measure each wire with an ohmeter, they should measure about 5000 ohms per foot. Look into the distributor cap for carbon tracks and look at the half round dimple in the center of the rotor for evidence of a carbon track. Replace cap and rotor if you question them.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Always include the year vette you are asking help for! At night in the dark, turn off the underhood lights and engine idling, look for sparks along each plug wire. Replace missing or broken wire looms, dress the plug wires so they do not touch metal. Plug wires have microscopic pinholes in them and can spark through these holes to metal. Measure each wire with an ohmeter, they should measure about 5000 ohms per foot. Look into the distributor cap for carbon tracks and look at the half round dimple in the center of the rotor for evidence of a carbon track. Replace cap and rotor if you question them.
Oops, sorry about that. I usually do put the year in. It's a '96 LT1 so as you probably know I can't just look into the Dis. cap. The wires are a year old and I have already done the misting trick. I appreciate your answer though.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Above idle it runs good. I have been chasing this idle issue for some time now. I made some headway yesterday by enlarging the lower hole on the TPS so I could cheat on the adjustment for it a little. That seemed to help. Also when the engine is stone cold it has a hesitation when you rev it up slightly. After it warms up it is gone. I've never had this low resolution code before. I know multiple misfires on a scan are a characteristic of the LT1 but I just thought it odd they are on these two cylinders all the time, no others. I suppose they could be false. I just wanted to throw it out there for you guys. This scan was an idle only scan for about 10 minutes. I have checked the adjustment on the IAC several times and it appears to working properly. Not on this scan but the one before I had a PO300 Random Misfires Detected. I cleared that and so far has not returned.
Last edited by Weav's Vet; May 11, 2009 at 12:25 PM.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Random or multiple cylinder misfires are usually fuel related (injectors) and at idle, the TPS has zero to do with how much fuel they squirt. Out here, your Year is covered by a special 200K warranty which was issued to avoid a CARB recall (even though the problem was traced to the fuel additive MTBE which is long since banned). I'd have them cleaned at a shop that has the right equipment to do so, but you might just check the hot and cold resistance of the injector coils at the offending cylinders first. Should be around 15 to 17 ohms.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Random or multiple cylinder misfires are usually fuel related (injectors) and at idle, the TPS has zero to do with how much fuel they squirt. Out here, your Year is covered by a special 200K warranty which was issued to avoid a CARB recall (even though the problem was traced to the fuel additive MTBE which is long since banned). I'd have them cleaned at a shop that has the right equipment to do so, but you might just check the hot and cold resistance of the injector coils at the offending cylinders first. Should be around 15 to 17 ohms.
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Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Hopefully it turns out to be something else. You know how one thing can affect the other on these engines.
