Need quick help! LT4 is Backfiring!
Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
Need quick help! LT4 is Backfiring!
Ok, so all I've done is take my shorty headers off, the entire catback, the AIR system, and R&R the plugs and wires. Now, with just headers on, it backfires! I do have the hole on the back of the intake open still (haven't made a plate to cover it yet). So... it has a very large vacuum leak. Could that cause backfiring? I plan on having the exhaust shop cut out a plate to bolt up to there.
I'm having the car towed to the exhaust shop tomorrow to have custom 3" exhaust built and would like to figure out what's going on before it's over there. Don't want to have to tow it back to the garage here.
I'm having the car towed to the exhaust shop tomorrow to have custom 3" exhaust built and would like to figure out what's going on before it's over there. Don't want to have to tow it back to the garage here.
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A large enough intake leak could cause the problem you describe. I'd still double check plug wires though.
Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
Originally Posted by Nathan Plemons
Open headers will obviously pop and crackle, but it's not a true backfire. I'd say that huge hole in the back of your intake isn't helping anything, it's got all of your calibrations messed up.
Yeah, I agree. I double checked wires again and they are correct.
I had it towed over to the exhaust shop and i'm having my guy make a plate to cover the AIR system hole on the back of the intake. I'm pretty sure that because it probably can't pull a vaccum at all that's why it was backfiring. Just headers will obviously make it sound worse too.
I ran the '94 with the 383 once with just the manifolds on.. wow was that one loud!!! 11.55:1 compression is not friendly to your ear drums
..Anyway, i'll let you guys know what happens. I should have a kick *** exhaust and everything setup by tomorrow afternoon
Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
DOH! ok, well the problem turned out to be wires 5 & 7 were reversed.... exhaust guy got it up on the rack and was able to trace the wires better. Man do I hate the design of all that stuff on the front/driver's side of the engine. I followed the wires pretty well and thought they were right!
Backfire is fixed and exhaust work is under way!
Backfire is fixed and exhaust work is under way!
Last edited by GlockLT4; Dec 1, 2004 at 12:43 PM.
Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
Originally Posted by SLOWRIDE
Glad you found it. Hope she sounds great. 
. Figured it would be a slim chance since all i did was change headers though.
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Thread Starter
Team Owner
Joined: Apr 2001
Posts: 22,267
Likes: 3
From: Dallas TX
Originally Posted by bogus
you need an LTCC conversion. that will make running plug wires REAL easy...
that will make running plug wires REAL easy... haha.. yeah, or i could pay my exhaust guy to figure it out for a lot less than the LTCC