backfiring closed loop only?
Thread Starter
Melting Slicks
Joined: Jun 2002
Posts: 2,152
Likes: 243
From: Northern VA
backfiring closed loop only?
What would cause this problem? I was out cruising and it felt like the tune was slowly getting fatter and fatter. I started feeling some backfiring in the headers. At light throttle in 5th gear, It would buck initially until It went open loop. Starting from stop and mashing it (open loop) it seems fine. I have had a similar problem before caused by a header leak introducing air to 02 sensor. Exhaust looks ok this time. What gives? P.S. I am speed density and DFI 
Burning Brakes
Joined: Nov 2001
Posts: 812
Likes: 1
From: Sherman Texas
My 89 GTA did something very similar right before the Mass Aiflow sensor went out. Took me a couple days to find it as it would run fine and never set a code, and then just lose power on the highway after I had cruised for a little bit. If you have a spare, swap em and see.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
Originally Posted by jerkyboy
What would cause this problem? I was out cruising and it felt like the tune was slowly getting fatter and fatter.
Last edited by mseven; Mar 8, 2006 at 10:04 PM.
Thread Starter
Melting Slicks
Joined: Jun 2002
Posts: 2,152
Likes: 243
From: Northern VA
I didn't have a chance to datalog yesterday as I had my hands full running the curves on skyline drive 
The car wasn't doing this before I uncorked my exhuasts last week (took out crimped bends, replaced with mandrel bends). Let me ask you this, if they guy was welding on my exhaust and ground his welder on the the exhaust, could it have fubar'd the O2 sensor?
The only other thing I have done recently is remove the TB. Even a gasket leak at this location should not affect a speed density system right???
The car wasn't doing this before I uncorked my exhuasts last week (took out crimped bends, replaced with mandrel bends). Let me ask you this, if they guy was welding on my exhaust and ground his welder on the the exhaust, could it have fubar'd the O2 sensor?
The only other thing I have done recently is remove the TB. Even a gasket leak at this location should not affect a speed density system right???
Melting Slicks
Joined: May 2002
Posts: 2,670
Likes: 4
From: Severna Park MD
Originally Posted by jerkyboy
I didn't have a chance to datalog yesterday as I had my hands full running the curves on skyline drive
The car wasn't doing this before I uncorked my exhuasts last week (took out crimped bends, replaced with mandrel bends). Let me ask you this, if they guy was welding on my exhaust and ground his welder on the the exhaust, could it have fubar'd the O2 sensor?
The only other thing I have done recently is remove the TB. Even a gasket leak at this location should not affect a speed density system right???
The car wasn't doing this before I uncorked my exhuasts last week (took out crimped bends, replaced with mandrel bends). Let me ask you this, if they guy was welding on my exhaust and ground his welder on the the exhaust, could it have fubar'd the O2 sensor?
The only other thing I have done recently is remove the TB. Even a gasket leak at this location should not affect a speed density system right???
I viewed the tape and unfortunately the runs up the east side just don't look as fast as they were. That east side is hairy, especially with the gravel and sand on the road from the salt trucks.
I didn't wreck and you didn't break down. Success!!!
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Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
Originally Posted by jerkyboy
The car wasn't doing this before I uncorked my exhuasts last week (took out crimped bends, replaced with mandrel bends). Let me ask you this, if they guy was welding on my exhaust and ground his welder on the the exhaust, could it have fubar'd the O2 sensor?
The only other thing I have done recently is remove the TB. Even a gasket leak at this location should not affect a speed density system right???
The only other thing I have done recently is remove the TB. Even a gasket leak at this location should not affect a speed density system right???
Thread Starter
Melting Slicks
Joined: Jun 2002
Posts: 2,152
Likes: 243
From: Northern VA
I pulled the o2 sensor and the tip was white. That means that side is running lean correct? I can smell it running rich though. That's wierd. I heard some rattle noise in the end of the sensor. Is that normal?
I reset the TPS values in my DFI. I am not sure what to look at as far as IAC counts. I need to research more.
I could not find any vacuum leaks or unplugged lines? I'm going to replace the o2 sensor. It is a four wire with a #3302 on the side. Anyone know where I can get this particular 02?
I reset the TPS values in my DFI. I am not sure what to look at as far as IAC counts. I need to research more.
I could not find any vacuum leaks or unplugged lines? I'm going to replace the o2 sensor. It is a four wire with a #3302 on the side. Anyone know where I can get this particular 02?
Thread Starter
Melting Slicks
Joined: Jun 2002
Posts: 2,152
Likes: 243
From: Northern VA
Yeah..what's a fish bite feel??
Alvin, on part throttle I actually feel little backfires in what seems to be the headers. Does that follow with a lean condition? My headers were getting hot as well.
Everything was ok until I freed up my exhaust then all of a sudden I'm getting this stuff.
Would my freed up exhaust be scaveging (sp) better and causing this lean condition? The only backpressure I have now are my flowmasters.
P.S. When are you going to come down to NOVA for a dyno tune session?
Alvin, on part throttle I actually feel little backfires in what seems to be the headers. Does that follow with a lean condition? My headers were getting hot as well.
Everything was ok until I freed up my exhaust then all of a sudden I'm getting this stuff.
Would my freed up exhaust be scaveging (sp) better and causing this lean condition? The only backpressure I have now are my flowmasters.
P.S. When are you going to come down to NOVA for a dyno tune session?
