[b]tune gone bad?[/b]
[b]tune gone bad?[/b] I had my 02' Ls1 dyno-tuned almost a year ago/5k. It ran awesome for a few months and then started to miss-fire intermittently. Recently it got worse and now backfires through tail pipe, especially when decelerating in D, 3 , 2 or 1. I have replaced wires, plugs, injectors, coil pack, O2 sensors, fuel filter and more trying to fix this. It gave a PO300 code a while back, but nothing lately. Could the timing be off due to the tune after about 5k miles??? I am taking extra therapy sessions to deal with this. Please help. Please?
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Seemed like I chased a problem like this about a year ago. Did everything you did (mechanically) and still had a problem.
It really was not until I went the tuning route that I got it solved. With a wideband and some logging, discovered Trims were averaging +15..it was essentially running too lean.
The dyno tune may not have addressed the areas of driving where you are experiencing difficulties. Car may run great at WOT on a dyno, but more modifications you add..more airflow required.
If decelerating, are you sure it is not just the 'normal' fuel cut off 'backfire' from the exhaust? Other than that, the only thing that can usually drift with time on a tune are your Trims, especially as temperatures change . If they become excessive and your LTrims exceed a certain point, you can start getting that random lean misfire.
I would check that out. Good luck.
..WeathermanShawn..
It really was not until I went the tuning route that I got it solved. With a wideband and some logging, discovered Trims were averaging +15..it was essentially running too lean.
The dyno tune may not have addressed the areas of driving where you are experiencing difficulties. Car may run great at WOT on a dyno, but more modifications you add..more airflow required.
If decelerating, are you sure it is not just the 'normal' fuel cut off 'backfire' from the exhaust? Other than that, the only thing that can usually drift with time on a tune are your Trims, especially as temperatures change . If they become excessive and your LTrims exceed a certain point, you can start getting that random lean misfire.
I would check that out. Good luck.
..WeathermanShawn..
Thanks, that's what I will try next. The backfire happens more than once, and I am off the throttle completely; "bang.............pop...............bang". None of this happened till after a few thousand miles later. Then slowly it miss fired on occasion. Now it is worse. If I disconnect the battery, and re-connect after a few days, it runs better sometimes. It is really random, but getting worse. It also feels like it's lost substantial HP.
Last edited by TedsB4Csled; Apr 27, 2009 at 05:14 PM.
