Backfire on Acceleration.
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Backfire on Acceleration. 2005 lm7 5.3l
chopacabra cam
With springs
Tuned on e85
straight pipe with headers
Fuel pressure is at 58psi
When idling or crusing it runs perfectly fine but i try to give it alot Throttle it back fires thro intake. It randomly started after fueling up. Need some help with this
chopacabra cam
With springs
Tuned on e85
straight pipe with headers
Fuel pressure is at 58psi
When idling or crusing it runs perfectly fine but i try to give it alot Throttle it back fires thro intake. It randomly started after fueling up. Need some help with this
Backfiring through intake is intake valve related MOST of the time. I’d start by pulling the valvecovers and looking for a broken spring/retainer/lock or possibly youve bent an intake valve via piston contact….maybe an overrev….and it can’t fully close now. Thats where I’d start anyway. A leak-down test will confirm valve sealing. If all is good there, I’d go to data-logging while driving and look at that side of the issue.
Teching In
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Backfiring through intake is intake valve related MOST of the time. I’d start by pulling the valvecovers and looking for a broken spring/retainer/lock or possibly youve bent an intake valve via piston contact….maybe an overrev….and it can’t fully close now. Thats where I’d start anyway. A leak-down test will confirm valve sealing. If all is good there, I’d go to data-logging while driving and look at that side of the issue.
Could bad e85 cause backfire? My truck is only tuned for 87 and e85
Teching In
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Or it has so much extra timing in the FF and multiplier tables, it's lighting the plug off before the intake valve is closed.
I do not see how water in the fuel would make it backfire out of the intake.
The intake valve has to be open for that to happen.
I do not see how water in the fuel would make it backfire out of the intake.
The intake valve has to be open for that to happen.
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update i smell fuel in oil, im guessing bad injector now
Last edited by Brodrdude; Mar 27, 2024 at 02:45 AM.
The timing would have to be how far advanced to actually ignite before the intake valve closes????? That sounds absurd if it was running fine and this suddenly happened right after refueling
Teching In
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Was driving it all day hauling **** was driving perfectly normal. Until I fueled up, soon I left the gas station it started popping
Run through the tank and fill up with 87 and see what happens. If it drives normal, there you go. Always go back to the last things you did. Liljay is right, though. Check your timing tables on E.
Chevelle is also right, backfire on accel is intake valve related. If problem persists after swapping fuel, pull the heads.
Chevelle is also right, backfire on accel is intake valve related. If problem persists after swapping fuel, pull the heads.
Teching In
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Run through the tank and fill up with 87 and see what happens. If it drives normal, there you go. Always go back to the last things you did. Liljay is right, though. Check your timing tables on E.
Chevelle is also right, backfire on accel is intake valve related. If problem persists after swapping fuel, pull the heads.
Chevelle is also right, backfire on accel is intake valve related. If problem persists after swapping fuel, pull the heads.
Teching In
Joined: Feb 2024
Posts: 11
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Run through the tank and fill up with 87 and see what happens. If it drives normal, there you go. Always go back to the last things you did. Liljay is right, though. Check your timing tables on E.
Chevelle is also right, backfire on accel is intake valve related. If problem persists after swapping fuel, pull the heads.
Chevelle is also right, backfire on accel is intake valve related. If problem persists after swapping fuel, pull the heads.
Another thing is make sure the FF is actually working and reading properly.
If it's not, that will cause a very lean condition, but you would know because it would run like *** all the time.
Do you have a way to data log it?
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The flex fuel sensor. It detects the amount of ethonal in the fuel, it adjusts the stoich value and can add additional timing.
Another thing is make sure the FF is actually working and reading properly.
If it's not, that will cause a very lean condition, but you would know because it would run like *** all the time.
Do you have a way to data log it?
Another thing is make sure the FF is actually working and reading properly.
If it's not, that will cause a very lean condition, but you would know because it would run like *** all the time.
Do you have a way to data log it?
Before..