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Really bad misfire and not sure why

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jakk220

15+ Year Contributor
1,320
320
Nov 13, 2010
Akron, Ohio
Not too long ago I developed a random misfire/sputter out of no where. It only happens under anything past about 3/4 throttle. Checked for boost leaks and only had a tiny one at the throttle body but nothing serious. I pulled my spark plugs and they were white. I dont have a wideband but had the a/f spot on about 2 months ago when i used my buddies to tune my car.

I bumped the fuel up to about 21% fuel and then for about 6 pulls or so the misfire was gone or very small. So i thought i fixed it until it came back with more force. I have no idea what it was but my car bucked so hard i honestly think my neck is going to hurt tomorrow. It felt like i hit a wall.

Fuel filter was just replaced, checked spark plug gap and its at .28, checked wires and there good, no fuel leaks. I was seeing some really high injector duty cycles at about 108% at 6k and about 70 at 4k. I have 680cc injectors. i will have a log of this up soon but i really need help bad. ive tried so many things and now im lost. also no DTC's except random misfire

Scratch the part about the hardcore bucking. It's still misfiring but I fixed the break your neck ordeal but I can honestly say I'm imbarased to say what it was.
 
Well I brought the duty cycles down by putting back on my stock fpr but its still missing. And thanks I'll look into it

Here is the log of the misfire. Anything stand out? Its at about 101 seconds
 

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