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bad back fire

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Old 12-02-2010, 08:02 AM   #1
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Default bad back fire

ok guys need some real help. i had my computer sent out and tuned to my mods because i am not near any shops. i plugged everything in and it fired up and idled great. i only had shorty headers on so i did not rev it at all. i saw some flames shot every once and a while. after fabbing my exhaust i put it on and fired it up. it started great but every minute or so it would back fired really bad and just exploded my driver side muffler. i noticed one of the injectors on the driver side had bad o-ring. so i replaced, unplugged the battery for a couple of days to reset it and fired it up again. it idled ok but as soon as i revved it, it back fired real bad again, these back fires are ear popping i mean bad. any suggestions?
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Old 12-02-2010, 09:54 AM   #2
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valve not hanging open is it???

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Old 12-03-2010, 10:56 PM   #3
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nope sure not. any other suggestions?
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Old 12-10-2010, 11:18 PM   #4
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Default backfire

check your O2 sensors with a scan tool to make sure they are working correctly, I had this same exact problem after my 6.0 swap. well except for the exploding muffler part. Turned out O2 sensor was stuck on lean and it was loading up my exhaust. Hope this helps
2000 GMC Sierra Z71 6.0 LQ9, Mahle Forged Flatops, Comp 208/212-554/558 115 LSA, LS6 Valvesprings, Harland Sharp Roller Rockers,NGK TR55 plugs, MSD wires, Melling High Volume/Pressure oil pump, Arp main studs-rod bolts-head bolts, Nelson's 93 Octane Tune, rear 02's and Egr Delete
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Old 12-12-2010, 02:28 PM   #5
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Backfiring in the exhaust like that requires raw fuel and free oxygen.
A rich condition combined with an exhaust leak or a misfiring cylinder can cause this sort of thing. The oxygen is either coming from an exhaust leak or a cylinder that isn't firing.
The extra fuel could be from one cylinder not firing, or from the entire bank running too rich.
I would look at the pulse-widths for each bank, along with your fuel trims -assuming you are running with adaptive fueling active.
Of course I'd also check for the exhaust leaks.
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Old 12-12-2010, 04:06 PM   #6
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also check or replace your plugs and wire.also check the MAP sensor.
2000 WS6,346,TFS 220,fast92/92,EPS cam,A4, CIR-D 3600 stall,3.25 9"Moser,BMR,UMI,SPHOON.MONEY PIT 3.

Last edited by garygnu; 12-12-2010 at 05:02 PM.
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