LT1 Misfiring - again
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,972
Likes: 243
LT1 Misfiring - again
94 LT1/ZF6
It is misfiring a bit under load. This includes giving it some gas at low rpm in high gear - you know the situation where you should really be a gear lower but you know it has the torque to do it. It will also misfire at high rpm - say your stretching the LT1s legs out. This just started today. The last time it had this problem was when the ICM was bad and the misfire wouldn't show up until the engine was hot. I noticed today's misfire at a low rpm load (even in 1st gear @ 1500rpm) on a cold motor. Also, I do have the ICM bracket spaced away from the cylinder head with a few washers to help avoid heatsoak.
The motor did this once before and I replaced the ICM and all was well. That ICM is now about one month old. The plugs and wires have less than 3k on them. I had the plugs out just this past weekend and they all looked good. The opti I'd almost venture to say is original with 107k on it. I know many will jump to say opti but I just don't know. Under 'normal' driving there is no misfire. Just heavy loads at low and high rpm. No codes. Thoughts? Things to try?
It is misfiring a bit under load. This includes giving it some gas at low rpm in high gear - you know the situation where you should really be a gear lower but you know it has the torque to do it. It will also misfire at high rpm - say your stretching the LT1s legs out. This just started today. The last time it had this problem was when the ICM was bad and the misfire wouldn't show up until the engine was hot. I noticed today's misfire at a low rpm load (even in 1st gear @ 1500rpm) on a cold motor. Also, I do have the ICM bracket spaced away from the cylinder head with a few washers to help avoid heatsoak.
The motor did this once before and I replaced the ICM and all was well. That ICM is now about one month old. The plugs and wires have less than 3k on them. I had the plugs out just this past weekend and they all looked good. The opti I'd almost venture to say is original with 107k on it. I know many will jump to say opti but I just don't know. Under 'normal' driving there is no misfire. Just heavy loads at low and high rpm. No codes. Thoughts? Things to try?
Racer
Joined: Mar 2010
Posts: 291
Likes: 1
From: Temecula Cali
94 LT1/ZF6
It is misfiring a bit under load. This includes giving it some gas at low rpm in high gear - you know the situation where you should really be a gear lower but you know it has the torque to do it. It will also misfire at high rpm - say your stretching the LT1s legs out. This just started today. The last time it had this problem was when the ICM was bad and the misfire wouldn't show up until the engine was hot. I noticed today's misfire at a low rpm load (even in 1st gear @ 1500rpm) on a cold motor. Also, I do have the ICM bracket spaced away from the cylinder head with a few washers to help avoid heatsoak.
The motor did this once before and I replaced the ICM and all was well. That ICM is now about one month old. The plugs and wires have less than 3k on them. I had the plugs out just this past weekend and they all looked good. The opti I'd almost venture to say is original with 107k on it. I know many will jump to say opti but I just don't know. Under 'normal' driving there is no misfire. Just heavy loads at low and high rpm. No codes. Thoughts? Things to try?
It is misfiring a bit under load. This includes giving it some gas at low rpm in high gear - you know the situation where you should really be a gear lower but you know it has the torque to do it. It will also misfire at high rpm - say your stretching the LT1s legs out. This just started today. The last time it had this problem was when the ICM was bad and the misfire wouldn't show up until the engine was hot. I noticed today's misfire at a low rpm load (even in 1st gear @ 1500rpm) on a cold motor. Also, I do have the ICM bracket spaced away from the cylinder head with a few washers to help avoid heatsoak.
The motor did this once before and I replaced the ICM and all was well. That ICM is now about one month old. The plugs and wires have less than 3k on them. I had the plugs out just this past weekend and they all looked good. The opti I'd almost venture to say is original with 107k on it. I know many will jump to say opti but I just don't know. Under 'normal' driving there is no misfire. Just heavy loads at low and high rpm. No codes. Thoughts? Things to try?
Rob
Heel & Toe
Joined: Apr 2006
Posts: 21
Likes: 0
From: Texas
I'm in the same boat. It misses under load under 2000 rpm. What's the ICM, idle control module? I'll check mine out. Any tips on replacing it if I go that route?http://forums.corvetteforum.com/c4-t...-no-codes.html
Racer
Joined: Mar 2010
Posts: 291
Likes: 1
From: Temecula Cali
I'm in the same boat. It misses under load under 2000 rpm. What's the ICM, idle control module? I'll check mine out. Any tips on replacing it if I go that route?http://forums.corvetteforum.com/c4-t...-no-codes.html
Rob
Instructor
Joined: Aug 2001
Posts: 110
Likes: 0
From: Wichita KS
on my 96 lt1 camaro, i am having same problems, and i have already replaced ICM and plugs, doing the opti next just waiting on the mail. I also checked fp first, and i was getting good pressure, and on the scanner i was showing lean and having random misfires. i believe my problem to be the opti, i should find out this week.
thanks
matt
thanks
matt
Racer
Joined: Mar 2010
Posts: 291
Likes: 1
From: Temecula Cali
on my 96 lt1 camaro, i am having same problems, and i have already replaced ICM and plugs, doing the opti next just waiting on the mail. I also checked fp first, and i was getting good pressure, and on the scanner i was showing lean and having random misfires. i believe my problem to be the opti, i should find out this week.
thanks
matt
thanks
matt
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,972
Likes: 243
I believe it is ignition control module.
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Racer
Joined: Mar 2010
Posts: 291
Likes: 1
From: Temecula Cali
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Last edited by chileverde; Jun 23, 2010 at 10:55 PM.
