Backfire and popping
Thread Starter
TECH Enthusiast
Joined: Jun 2010
Posts: 611
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From: Illinois
Backfire and popping Background:
Recently, my ls1 #6 cylinder cracked and water basically mixed with the oil and got everywhere. Upon removing the engine, the water-oil mix came out of the intake manifold and exhaust manifolds along with the y pipe. I dropped in a new lq9 and swapped everything over to the new block. We got the car running a few days ago and there are no lights on, everything sounds good, no missfires etc.
Issue:
After breaking it in for 2 or 3 days I decided to get on it in first gear and the car backfired hard, there was a loud pop and then the car itself stalled. I pulled over checked under to make sure there was no oil etc and say the y-pipe popped loose. So I started it back up and drove it home with open headers, reattached it and it has driven fine for the past 2 days. However, I just got on it again and the same thing happened, backfire, pop then stall. Started it back up and drove home.
Question:
Would going up the extra .3 liters affect the original tune done by Speed Inc., and need to get retuned, or could that oil-water mix have been blown into the muffler where it is now trapped and causes too much back pressure which would mean I would need to get a new muffler. The muffler is a flowmaster 40 series. Or does anyone else see any other issues. The car runs great driving around etc, but has this issue once it sees 6k RPM's
Recently, my ls1 #6 cylinder cracked and water basically mixed with the oil and got everywhere. Upon removing the engine, the water-oil mix came out of the intake manifold and exhaust manifolds along with the y pipe. I dropped in a new lq9 and swapped everything over to the new block. We got the car running a few days ago and there are no lights on, everything sounds good, no missfires etc.
Issue:
After breaking it in for 2 or 3 days I decided to get on it in first gear and the car backfired hard, there was a loud pop and then the car itself stalled. I pulled over checked under to make sure there was no oil etc and say the y-pipe popped loose. So I started it back up and drove it home with open headers, reattached it and it has driven fine for the past 2 days. However, I just got on it again and the same thing happened, backfire, pop then stall. Started it back up and drove home.
Question:
Would going up the extra .3 liters affect the original tune done by Speed Inc., and need to get retuned, or could that oil-water mix have been blown into the muffler where it is now trapped and causes too much back pressure which would mean I would need to get a new muffler. The muffler is a flowmaster 40 series. Or does anyone else see any other issues. The car runs great driving around etc, but has this issue once it sees 6k RPM's
Thread Starter
TECH Enthusiast
Joined: Jun 2010
Posts: 611
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From: Illinois
Cats are gone along with all the emissions stuff (egr and air). I just checked the intake plumbing and everything seems to check out. I'll just baby the car until I can get it into Speed Inc. again. I gotta ask though, why would the intake plumbing cause backfire issues and popping?
Cats are gone along with all the emissions stuff (egr and air). I just checked the intake plumbing and everything seems to check out. I'll just baby the car until I can get it into Speed Inc. again. I gotta ask though, why would the intake plumbing cause backfire issues and popping?
Good that you don't have cats.
It almost sounds as if the car is lean popping. If there's any way you can send me a log whenever you get the car to re-tuned, I'd like to have a look at it.
Stock cam and springs? Springs could cause that as well, and so could the intake if it isn't sitting correctly on the cylinder heads which would create an air leak around the intake gaskets. It's highly improbable, but just stuff to check.
Thread Starter
TECH Enthusiast
Joined: Jun 2010
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From: Illinois
thank you for the info, that was really helpful. I have to call Speed Inc. to try and schedule a re-tune, however, it's probably going to be a bit of time before I can get it there since they are usually extremely busy. the lq9 received 243 heads and a 2004 zo6 cam, so the lift on it is .551/.549 I believe. The springs are good to .575
I will actually try another set of injectors and while i'm there, make sure there isn't any noticeable leaks around the intake while the car is running
I will actually try another set of injectors and while i'm there, make sure there isn't any noticeable leaks around the intake while the car is running
thank you for the info, that was really helpful. I have to call Speed Inc. to try and schedule a re-tune, however, it's probably going to be a bit of time before I can get it there since they are usually extremely busy. the lq9 received 243 heads and a 2004 zo6 cam, so the lift on it is .551/.549 I believe. The springs are good to .575
I will actually try another set of injectors and while i'm there, make sure there isn't any noticeable leaks around the intake while the car is running
I will actually try another set of injectors and while i'm there, make sure there isn't any noticeable leaks around the intake while the car is running
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Thread Starter
TECH Enthusiast
Joined: Jun 2010
Posts: 611
Likes: 0
From: Illinois
i stopped driving it so i don't hurt anything. It's just a precaution, but I'm hoping I can get a retune without pulling out $500 again. Tomorrow I'm going to put the other injectors in and then plug in my programmer to read the timing etc. I'm no tuning expert so I won't mess with it, I just want to see if it will be where it should be, or if it's off at all.
