LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Weird misfire down low \=

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Old Aug 21, 2008 | 11:37 AM
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Default Weird misfire down low \=

My car has had this problem for a while, and I've changed numerous things thinking I'll figure it out. Anywho, I recently got the car running after a heads swap, and for some reason (randomly) the car will backfire through the intake if I quickly give it throttle to accelerate faster. If I ease on the the throttle it's fine. This typically happens at a low RPM, usually when accelerating from a stop or if I'm traveling at a low RPM.. It's so weird. I've changed the coil, icm, opti, wires, plugs (are only 3 weeks old), injectors, car throws no codes, etc. I'm pretty stumped. Any ideas?
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Old Aug 21, 2008 | 11:48 AM
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just an idea but you could unplug your MAF and rule that out too.What about the TPS sensor? check the voltage there also
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Old Aug 21, 2008 | 11:58 AM
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Originally Posted by lt170chevelle
just an idea but you could unplug your MAF and rule that out too.What about the TPS sensor? check the voltage there also
No MAF here. I have speed density
one less thing to worry about lol
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Old Aug 21, 2008 | 01:00 PM
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cam degreed correctly? too much cam timing one way or other?
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Old Aug 21, 2008 | 01:15 PM
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......

Last edited by Andys94Z; Aug 21, 2008 at 09:35 PM.
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Old Aug 21, 2008 | 03:28 PM
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Originally Posted by LT1FirebirdSLP
cam degreed correctly? too much cam timing one way or other?
Cam wasn't changed and car rean great before

Originally Posted by Andys94Z
my cousins TPI firebird did that for a while, on a brand new motor

turned out there was a 1/4 inch long chunk of the headgasket missing inbetween two cylinders. looked like someone cut it out with a razor blade? but the gaskets were brand new so?

not saying thats what it is, but you never know
Nah, it's a stupid ignition problem that I can't trace. )=
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Old Aug 21, 2008 | 10:07 PM
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Sounds quite similar to my problem, unsolved as of yet. Was run on dyno and ignition scope, the shop found nothing, though they could not get it to miss on that day.

Just because you think it's ignition related, doesn't mean it is, don't paint yourself into a corner, you'll have less likely of a chance of figuring it out.
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Old Aug 21, 2008 | 11:28 PM
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Ignition/fuel. It's something. I have a bad lifter, could a lifter be causing anything related to this?
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Old Aug 21, 2008 | 11:39 PM
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Originally Posted by 1badzee
Ignition/fuel. It's something. I have a bad lifter, could a lifter be causing anything related to this?
Depends on how bad that lifter is, I think if it was THAT bad that its causing all of the above, then your going to hear it quite well also....

Would probably sound something like a hammer hitting the block
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Old Aug 21, 2008 | 11:47 PM
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Not like a hammer lol, but it's a loud *** tick. Very loud. I don't see how this would cause a low RPM backfire through the intake, and at high RPMs run fine
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Old Aug 21, 2008 | 11:57 PM
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Its going to have to be REAL bad for something like that to happen, but your right that would be near impossible if it clears up at high RPM.

Got something laying around to check your fuel pressure? Would be a good time to verify how that pump is working...
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Old Aug 22, 2008 | 12:00 AM
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I surely will check it, although it's about a 4 month old Holley 255lph unit
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Old Aug 22, 2008 | 12:19 AM
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Oh ok, if its new its not as important, but still good to know.

Out of curiosity, what kind of Opti did you put in there?
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Old Aug 22, 2008 | 11:52 AM
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A reman, but it ran the same before with a GM unit. It actually runs a bit better with this new Reman once but the low rpm backfriew through the intake is still there, and inly happens when i quickly tap the gas to accelerate quick
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Old Aug 22, 2008 | 12:15 PM
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I dont know man, I wouldent trust those remans... That could really be your problem, but usually if it is you will see codes before too long.
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Old Aug 22, 2008 | 12:20 PM
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Throws no codes unfortunately, so it makes it tougher to see what it is lol
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