'96 LT4 misfire
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Intermediate
Joined: Aug 2024
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From: Stewartstown, PA
2025 Corvette of the Year Finalist - Unmodified
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'96 LT4 misfire
I purchased the '96 about a year ago. At that time, it had a severe miss under moderate to heavy load in all gears at low rpm's. Mechanic said it needed a tune up and we went with that. New Opti, plugs, wires, coil and ignition control module. The fuel pump has been replaced as well after it failed... For the most part, the issue went away. However, I can still get it to miss slightly in higher gears when under 2K rpm's. (Once beyond 2K rpm's, car pulls like a torque monster with no misses...) Granted, if the car was an automatic, you'd never feel that because it would automatically downshift. However, being the **** car guy that I am, I'd like to figure this out. It does not appear to do this (as much) when cold. Could I be looking at a faulty sensor? Perhaps a knock sensor? The car does not ping under these conditions, just misses. Additionally, the computer has been modified to activate the fans with a 180 degree t-stat instead of a 195 degree. Frankly, the car never, ever gets over 190 degrees even on the hottest days while sitting in traffic. Not sure if that's applicable or not but wanted to mention it... Any help will be greatly appreciated! Thanks!!
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From: Cape Coral, Florida
When a mechanic says “you need a tuneup” he isn’t a diagnostician but will just change a bunch of parts hoping he might get lucky and fix your car…a good diagnostician will tell you exactly what’s causing your engine to misfire with one bad part…did he look at your injectors ??…may be a bad injector but without a fuel pressure gauge and a scan tool and an injector “pulser” you won’t be able to accurately identify a faulty one.
Thread Starter
Intermediate
Joined: Aug 2024
Posts: 46
Likes: 9
From: Stewartstown, PA
2025 Corvette of the Year Finalist - Unmodified
2024 C4 of the Year Winner - Unmodified
When a mechanic says “you need a tuneup” he isn’t a diagnostician but will just change a bunch of parts hoping he might get lucky and fix your car…a good diagnostician will tell you exactly what’s causing your engine to misfire with one bad part…did he look at your injectors ??…may be a bad injector but without a fuel pressure gauge and a scan tool and an injector “pulser” you won’t be able to accurately identify a faulty one.
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Joined: Sep 2013
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From: Cape Coral, Florida
It was interesting that even though the engine did not throw any codes initially, my mechanic's scanner indicated a problem with cylinder #5 prior to the tune-up, and did not indicate any issues with that cylinder after the tune-up. Having said that, I hear you and I've ordered a fuel injector pulser and pigtail so I can balance test all my fuel injectors myself. Thanks!
You will also need a fuel pressure gauge…I’m not saying that is the cause but is something to be looked at…if this is intermittent may be a little harder to diagnose…that is where a labscope comes in handy.
Thread Starter
Intermediate
Joined: Aug 2024
Posts: 46
Likes: 9
From: Stewartstown, PA
2025 Corvette of the Year Finalist - Unmodified
2024 C4 of the Year Winner - Unmodified
I have a fuel pressure gauge so I'm good there. And it's not intermittent; I can reproduce it at will. Thanks!
