Help me if you can!!

nuuumb · 09-25-2012, 08:26 PM

I have an '05 C6 LS2 A4 with approx. 75,000 mi. 2 days ago i was passing someone and put my foot deep in the gas pedal. The car responded great as usual but right before I was going to let off of the accelerator (total time on floor approx. 4 seconds) I heard and felt a loud PPHHFFF! sound (like a carb would sound backfiring in the engine bay) and the car immediately started running horribly, like it's running on 5 cylinders. It's still running the same. Obvious finds, that may be unrelated, exhaust pipe had become seperated at one joint on one side where two peices join together. Spark plugs look ok...there is gas in the intake plenum. That's all the info I have...any ideas? thanks.

Ragtop 99 · 09-26-2012, 11:02 AM

Where the exhaust is separated, is it in front of the catalytic converters? If yes, the exhaust is sucking in outside air and could cause your O2 sensors to read incorrectly. That would then cause the motor to run the wrong AF mixture on that side.

nuuumb · 09-26-2012, 04:27 PM

I have catless resonators. But the seperation was just after the resonator on the passengers side and is only about 1 foot from the O2 sensor...

Hotrod · 09-26-2012, 05:12 PM

Check the MAF sensor, since you say you heard a slight backfire. This sensor is very sensitive and you may have blown it out from the backfire.

nuuumb · 09-27-2012, 06:25 AM

thanks, I'll check it. I looked at it quickly to see if there was major damage but i'll check to make sure the wires are intact. thanks

nuuumb · 09-27-2012, 01:31 PM

The MAF is intact so...

Ragtop 99 · 09-27-2012, 04:30 PM

Seal that leak and eliminate an easy possible problem.

Are you getting check engine light codes?

nuuumb · 10-01-2012, 12:23 PM

sorry for the delay Ragtop, I took both sides of the exhaust apart to verify that the resonator didn't come apart and damage the O2 sensor. My check engine light is already on due to installing headers and I haven't tuned it yet.

Ragtop 99 · 10-02-2012, 10:07 AM

I'd suggest reading the SES codes. Some autoparts places will do it for free.

nuuumb · 10-02-2012, 05:39 PM

thanks I'll do that and reply. I did find one plug with gasoline on it today; I apparently didn't pull that one at first. Is it possible that the coil on that plug went bad and is causing the problem??

09-25-2012, 08:26 PM	#1
nuuumb Smokin Member Join Date: Apr 2011 Location: Tuscaloosa, AL Posts: 15 My Gallery	Help me if you can!! I have an '05 C6 LS2 A4 with approx. 75,000 mi. 2 days ago i was passing someone and put my foot deep in the gas pedal. The car responded great as usual but right before I was going to let off of the accelerator (total time on floor approx. 4 seconds) I heard and felt a loud PPHHFFF! sound (like a carb would sound backfiring in the engine bay) and the car immediately started running horribly, like it's running on 5 cylinders. It's still running the same. Obvious finds, that may be unrelated, exhaust pipe had become seperated at one joint on one side where two peices join together. Spark plugs look ok...there is gas in the intake plenum. That's all the info I have...any ideas? thanks. Last edited by nuuumb; 09-26-2012 at 10:18 AM.

09-26-2012, 11:02 AM	#2
Ragtop 99 Smokin 1000HP Twin Turbo Club Join Date: Oct 2009 Location: Bethesda MD Posts: 1,552 My Gallery	Where the exhaust is separated, is it in front of the catalytic converters? If yes, the exhaust is sucking in outside air and could cause your O2 sensors to read incorrectly. That would then cause the motor to run the wrong AF mixture on that side. __________________ 2008 Atomic Orange Coupe 3LT, CC3, Z51 M6 LG Pros with cats, Vararam, 160 T-stat, DTE 3.90s, Elite tunnel plate, catch can, LG Wheels with 275 / 325 Invos, MGW Shifter, EPS 226/230 115 cam, HPT. Pfadt JOC suspension, Peak ported TB & IM. Gone but not forgotten: 2002 Camaro SS Droptop. cam, gears, etc. 11 sec 99 Z28 Vert, RIP.

09-27-2012, 04:30 PM	#7
Ragtop 99 Smokin 1000HP Twin Turbo Club Join Date: Oct 2009 Location: Bethesda MD Posts: 1,552 My Gallery	Seal that leak and eliminate an easy possible problem. Are you getting check engine light codes? __________________ 2008 Atomic Orange Coupe 3LT, CC3, Z51 M6 LG Pros with cats, Vararam, 160 T-stat, DTE 3.90s, Elite tunnel plate, catch can, LG Wheels with 275 / 325 Invos, MGW Shifter, EPS 226/230 115 cam, HPT. Pfadt JOC suspension, Peak ported TB & IM. Gone but not forgotten: 2002 Camaro SS Droptop. cam, gears, etc. 11 sec 99 Z28 Vert, RIP.

10-02-2012, 10:07 AM	#9
Ragtop 99 Smokin 1000HP Twin Turbo Club Join Date: Oct 2009 Location: Bethesda MD Posts: 1,552 My Gallery	I'd suggest reading the SES codes. Some autoparts places will do it for free. __________________ 2008 Atomic Orange Coupe 3LT, CC3, Z51 M6 LG Pros with cats, Vararam, 160 T-stat, DTE 3.90s, Elite tunnel plate, catch can, LG Wheels with 275 / 325 Invos, MGW Shifter, EPS 226/230 115 cam, HPT. Pfadt JOC suspension, Peak ported TB & IM. Gone but not forgotten: 2002 Camaro SS Droptop. cam, gears, etc. 11 sec 99 Z28 Vert, RIP.

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09-26-2012, 04:27 PM	#3
nuuumb Smokin Member Join Date: Apr 2011 Location: Tuscaloosa, AL Posts: 15 My Gallery	I have catless resonators. But the seperation was just after the resonator on the passengers side and is only about 1 foot from the O2 sensor...

09-26-2012, 05:12 PM	#4
Hotrod Smokin 1000HP Twin Turbo Club Join Date: Jun 2008 Location: A.C., NJ Posts: 1,392 My Gallery	Check the MAF sensor, since you say you heard a slight backfire. This sensor is very sensitive and you may have blown it out from the backfire.

09-27-2012, 06:25 AM	#5
nuuumb Smokin Member Join Date: Apr 2011 Location: Tuscaloosa, AL Posts: 15 My Gallery	thanks, I'll check it. I looked at it quickly to see if there was major damage but i'll check to make sure the wires are intact. thanks

09-27-2012, 01:31 PM	#6
nuuumb Smokin Member Join Date: Apr 2011 Location: Tuscaloosa, AL Posts: 15 My Gallery	The MAF is intact so...

10-01-2012, 12:23 PM	#8
nuuumb Smokin Member Join Date: Apr 2011 Location: Tuscaloosa, AL Posts: 15 My Gallery	sorry for the delay Ragtop, I took both sides of the exhaust apart to verify that the resonator didn't come apart and damage the O2 sensor. My check engine light is already on due to installing headers and I haven't tuned it yet.

10-02-2012, 05:39 PM	#10
nuuumb Smokin Member Join Date: Apr 2011 Location: Tuscaloosa, AL Posts: 15 My Gallery	thanks I'll do that and reply. I did find one plug with gasoline on it today; I apparently didn't pull that one at first. Is it possible that the coil on that plug went bad and is causing the problem??

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