Ls1 Popping and Backfiring! Please Help!
Thread Starter
Registered User
Joined: Jan 2017
Posts: 3
Likes: 0
From: Independence, Mississippi
Ls1 Popping and Backfiring! Please Help! First of all I'm new to this site so thanks in advance for any feedback.
2004 GTO LS1 I finally got to build
Car fired right up after build. I attributed backfiring to no tune. Got injectors and got her preliminarily tuned (hasn't made it to dyno yet) and still a backfire at random times. Will do it while idling once every 5-60 seconds. Misses/farts/backfires at certain rpm's during a pull, and will do a similar smooth pull later. Plugs are brown. Seems like it's getting the right amount of fuel and idles perfect. (Other than backfiring out exhaust.) It's super loud! 20ga loud! Lol. Tuner believes it to be electrical, not mechanical because of the randomness. Need to wrap this build up! Going back to school Thursday!
228r cam 112 lsa .600" lift
799 (243) heads ported and polished
Long tubes with cat-less mids
36lb injectors
LS-7 clutch
All new plugs and wires
2004 GTO LS1 I finally got to build
Car fired right up after build. I attributed backfiring to no tune. Got injectors and got her preliminarily tuned (hasn't made it to dyno yet) and still a backfire at random times. Will do it while idling once every 5-60 seconds. Misses/farts/backfires at certain rpm's during a pull, and will do a similar smooth pull later. Plugs are brown. Seems like it's getting the right amount of fuel and idles perfect. (Other than backfiring out exhaust.) It's super loud! 20ga loud! Lol. Tuner believes it to be electrical, not mechanical because of the randomness. Need to wrap this build up! Going back to school Thursday!
228r cam 112 lsa .600" lift
799 (243) heads ported and polished
Long tubes with cat-less mids
36lb injectors
LS-7 clutch
All new plugs and wires
TECH Regular
Joined: Apr 2015
Posts: 423
Likes: 2
From: Rochester, NY
After an engine build a few years ago, I found my backfiring was due to faulty MSD coil packs. Eight brand new coil packs to go along with the rest of the new engine, and 3-4 of them were faulty.
Real Nice! Returned them to MSD with a not so nice note, and got refunded.
Luckly, I kept my stockers, re-installed them, never looked back.
Real Nice! Returned them to MSD with a not so nice note, and got refunded.
Luckly, I kept my stockers, re-installed them, never looked back.
I saw a thread i while back, person had same issue. He had new plug wires and coils. Turnes out his plug wires were a bit too short and werent clamping on plugs. I bet its either a coil or plug wire issue.
you might be able to detect a misfire by un plugging each coil while the car is running and seeing if motor reacts to it. After finding a cylinder that dosent react differently with no spark, you can narrow it down. Id also check plug wire ohms
you might be able to detect a misfire by un plugging each coil while the car is running and seeing if motor reacts to it. After finding a cylinder that dosent react differently with no spark, you can narrow it down. Id also check plug wire ohms
Check to see that your coil sub harnesses are on the correct side.
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Thread Starter
Registered User
Joined: Jan 2017
Posts: 3
Likes: 0
From: Independence, Mississippi
Possibly found the culprit Thanks for the feedback! I think I found the culprit. A plug was cracked on the d/s. Whether it was arking off the head or just missing on that cylinder, I'm sure this has to be it. I was told to run a cooler plug with any powe increase anyway, so I'm going to the TR6GP's. TR5GP NGK stock. Any opinions on the 6?
