Backfire thru exhaust after header install
Thread Starter
Staging Lane
Joined: Nov 2004
Posts: 51
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Backfire thru exhaust after header install After installing headers, catted y and TSP catback the car backfires thru the exhaust when I shift (M6). It gets worse when the weather is cold and it only does it under heavy throttle, if I drive normal it doesn't backfire. Anyone else have this problem?
TECH Fanatic
Joined: Nov 2001
Posts: 1,379
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From: Holly Springs NC
My car backfires all the time, in between shifts on the street around 3500 or so and even after tossing it in neutral after a track run at the traps through 4th around 6600. But the strange thing is it doesn't do this between shifts at high RPM's while racing.
My Fiance thinks it sounds cool but I think it sounds likea jalopy! Funny how it doesn't do this with his PCM but it does with mine. And they've tuned the car but there is unspent fuel that's causing this.
I cannot recall this until I added headers, hell it will even create a few tiny backfires or subtle pops after starting it while it's running. I do think it got worse after my cam went in though. You can smell unburnt gas with cams and ORY's so your issue can be a tuning issue. Car is getting more air so with more power can cause the PCM to start tossing fuel thinking it's a bit more lean. Mine is obviously dumping more fuel somewhere with the RPM band and it wasn't dyno tuned with a wideband.............and getting the guys to do this is nearly impossible they don't think it's bad or annoying like I do
Weird **** but the car runs good #'s and traps nicely.
My Fiance thinks it sounds cool but I think it sounds likea jalopy! Funny how it doesn't do this with his PCM but it does with mine. And they've tuned the car but there is unspent fuel that's causing this.
I cannot recall this until I added headers, hell it will even create a few tiny backfires or subtle pops after starting it while it's running. I do think it got worse after my cam went in though. You can smell unburnt gas with cams and ORY's so your issue can be a tuning issue. Car is getting more air so with more power can cause the PCM to start tossing fuel thinking it's a bit more lean. Mine is obviously dumping more fuel somewhere with the RPM band and it wasn't dyno tuned with a wideband.............and getting the guys to do this is nearly impossible they don't think it's bad or annoying like I do
Weird **** but the car runs good #'s and traps nicely.
Last edited by racer88; Feb 16, 2006 at 01:16 PM.
Thread Starter
Staging Lane
Joined: Nov 2004
Posts: 51
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I think your right, it might need to be tuned. I also have an ls6 intake, port tb & maf so it's defenitly getting more air in and out now. I've been wanting to do a heads and cam so I'll wait and see if that happens before spending the money on a tune.
TECH Enthusiast
Joined: Jul 2005
Posts: 732
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From: Herndon, VA
Sounds great I think; it happens when the engine decelerates rapidly, especially when still cold. Mine was worse when I just had the Loudmouth, and got better after I added LTs and Cats. I have a 160* stat so I hear it all the time, but I love it. 
But I goose the throttle for hard down-shifting to take it easy on the clutch and help the synch. (This is normal behavior for LM owners, right?)
Try to visualize riding behind you at night and those pops are jets of flame...
...anyone see that mod where you stick spark plugs in the exhaust tips, and then pull a coil wire from #7 to dump raw gas down the exhaust and ignite it at the tail pipe. Dumb, I know; not advocating it, just providing an example of someone else obviously over the top, so you'll think I'm normal
Seriously, you might be a little rich, but I do like the sound...
But I goose the throttle for hard down-shifting to take it easy on the clutch and help the synch. (This is normal behavior for LM owners, right?)Try to visualize riding behind you at night and those pops are jets of flame...
...anyone see that mod where you stick spark plugs in the exhaust tips, and then pull a coil wire from #7 to dump raw gas down the exhaust and ignite it at the tail pipe. Dumb, I know; not advocating it, just providing an example of someone else obviously over the top, so you'll think I'm normal
Seriously, you might be a little rich, but I do like the sound...
My car used to backfire a little with the LM and stock manifolds. After I got headers, if I would get off the throttle at high rpms will still in gear, it would occassionally let some fire out the tips
