high end miss
Thread Starter
Teching In
Joined: Apr 2006
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high end miss it seems that at about 4500 rpm's my car seems to miss. do you think that it could be my fuel filter. it pisses me off. i only have 40k miles on my car. it makes sense to me because i run my car with not alot of gas alot. has anyone else had htis problem?
Usually fuel problems like you suspect present more as a bog or a loss of power.
I would look at ignition and valvetrain. With as much sitting as the car did and the fact that sitting long periods means valvesprings are compresses a LONG time some could be weak and floating.
I would look at ignition and valvetrain. With as much sitting as the car did and the fact that sitting long periods means valvesprings are compresses a LONG time some could be weak and floating.
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yaeh i would describe it as a bog. i was drunk when i wrote that last night haha. i took it out today and it didnt do it, but i bought a fuel filter anyways. The feeling is like when you hit the speed limiter, except your in first gear at 4500 rpm
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From: king of prussia, pa (home) and williamsport, pa (school)
same situation with me. do you have aftermarket plug wires? your one plug wire could be resting on a header primary, and that could cause it to randomly misfire. happened to me mostly at high rpms
Originally Posted by greenmachine94
no but i should probably change them soon.
Check the wire going from the opti to the ignition coil to make sure it has a good connection.
Finally -- check the harness on the passenger side of the intake manifold that goes from the PCM and then plugs down along the water pump and plugs into the optispark. Sometimes moisture and other things not very electrical friendly will just slowly kill the connection of that wiring harness.
If you haven't done plugs, wires, fuel filter -- I'd do that first and foremost.
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THis situation seems to be hit or miss when i step on hte gas. sometimes it runs fune. but 8 out of 10 times, right after 4.5k it seems like its sputtering. i looked at the harness to the opti, it looks a little dirty should i clean it wiht contact cleaner? the only thing that gets me is why does it only do it at those rpm's it isnt random, it runs 100% before i hit 4.5k?
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This is an extremely common problem and I've had it on every LT1 I've owned.
First thing to check is fuel, your injectors may be clogged, try some injector cleaner in the fuel tank. If that doesn't fix it, buy a fuel pressure gauge and check that, if it's bad the fuel pump may need to be replaced. If you haven't replaced the fuel filter in a long time do that.
If it's not fuel it's most likely ignition related. Namely, its either the plugs, wires, ignition coil, ICM module, or opti. Check each one and make sure you are getting spark across the coil ,opti, and plugs.
If it's not ignition it could be electrical (had this problem on my first lt1). Check to make sure the voltage is good, all of the grounds are connected properly, there are no frayed wires, etc.
If it's not any of those things, then you may need to start looking in the motor (bad valvetrain component, etc).
First thing to check is fuel, your injectors may be clogged, try some injector cleaner in the fuel tank. If that doesn't fix it, buy a fuel pressure gauge and check that, if it's bad the fuel pump may need to be replaced. If you haven't replaced the fuel filter in a long time do that.
If it's not fuel it's most likely ignition related. Namely, its either the plugs, wires, ignition coil, ICM module, or opti. Check each one and make sure you are getting spark across the coil ,opti, and plugs.
If it's not ignition it could be electrical (had this problem on my first lt1). Check to make sure the voltage is good, all of the grounds are connected properly, there are no frayed wires, etc.
If it's not any of those things, then you may need to start looking in the motor (bad valvetrain component, etc).
I had the same thing happen to my car. It ended up being the wire from the coil to the opti being corroded. I was pissed too because my car only had 60k on it. I swapped it out with a different one and it runs great now. Just a suggestion. Hope you find a solution.
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From: POULSBO WA.
I had the exact same problem, changed the plugs...wires...and had the gm top engine cleaner service done to the injectors at the dealership where I work. The crap you pour in the tank dosen't do any good at all. The injector service really smothed out the idle quality, and the missfire at 4500 rpm was gone.
he injector service really smoothed out the idle greatly
he injector service really smoothed out the idle greatly
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well 100 dollars later and 5 hours changing the plugs and wires, i found out it was where the ignition coil and opti connect. The part where the boot goes on was white with corrosion. you could see pitting where it was arching inside of the boot. i took a steel brush and cleaned it and it runs beatifully. some of the plugs were kind of worn. so i guess i got a tune up in the process. But thank you all for your help it is greatly appreciated.
