Stock internal bolt on car. On decel it backfires from the passenger side of the motor and when it does it has a huge Ltrim and Strim. Why would you have a big Trim numbers on decel? I was thinking DFCO but I dont think it ever kicks in since the MAP threshold is 10kpa and it never reaches it and its not set to enable until 285*s (stock setting).
On the log file, you can see it happening at frame 37 and 1613. Also, the B2O2 is screwy for some reason....
Last edited by Country Boy; 05-28-2007 at 06:09 PM.
My 01 Z06 is doing the same thing between shifts and sometimes on hard decel
I am thinking I may have an exhaust leak since my headers are slip fit. Altho I did replace one of the O2 sensors about 6 months ago.
It does not seem to affect my LTFTs at any other point luckily. Mine are about +2% B1 and +12% B2
well, I just got a call from the shop that is working on my car. Apparently I have 2 push rods mushroomed up against the rocker arms. I wonder if this has anything to do with the fuel trims. sure explains the phantom knock retard i picked up in yesterdays data log.
Backfire in the exhaust is a lean condition. Probably just before going into DFCO. Wideband will tell the whole story.
Always Support Our Troops!
but its only 1 side, not both. Its just the pass side where the trims are spiking, the drivers side is fine.
I tuned everything via a wideband. VE table and MAF table. I even put the VE back to stock up to .20. It started about 2 weeks after it was tuned. It didnt do it while I was tuning it or after I put it all back to CL.
When you have banks that far off there's a problem. BUT both sides are going lean based on the STFT's.
Always Support Our Troops!
When the backfire happens, B1 is only 2.3% STrim and 1.6% Ltrim How is that both going lean? B2 is Strim 20.3% and 11.7% Ltims...
The only thing I can think of is he cut and spliced both O2 wires and used butt connectors.
Look at the o2 voltage as well. STrims are a learned value. o2's are instantaneous. If you had a wideband you would know how much.
Always Support Our Troops!
Is it right for the B2S1 to be so irratic all the time? Somtimes it just flatlines and doesnt follow the B1S1 at all.
I'm sitting in a car right now (lumpy idle & procharger) that B1 is + 6 and B2 is -3...
Always Support Our Troops!
I mean the O2s, not the trims. The pass O2 dies (flatlines) for like 78 frames at some points and sometimes itll hang at ~900 for little bit.
When the backfire happens, the Ltrim is flatlined on the pass side for a long time in the 13.3 range while the drivers side is 1.6. That leads me to believe it isnt a tuning problem as wouldnt both sides be pegged and acting the same? Thats what I dont understand. Frame 0-75 show this as does frames 1560-1660.
AIR tubes cracked and allowing unmetered air? or maybe just a bad gasket?
Always Support Our Troops!
race headers. Im thinking its an air leak or bad O2 signal the way he cut and spliced the wires. He got cutouts in the Y too..
Definite possiblilty.
Always Support Our Troops!
just as an update for anyone with the same problem. I dug deeper. Took the top end apart, no problems. Come to my suprise, on the pass side header, every bolt was loose to the point of being able to turn them by hand and the last header bolt was missing. The drivers side was the same way.
Installed a new header bolt and tighetend everything down and all is well again.
Thanks for the help!
Reply With Quote