Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Have an issue I'm hoping I can get some insight to. Vehicle is a 2001 Chevy Tahoe with a 650+hp supercharged 6.0 LQ9. I swapped the engine about 12 yrs ago and it's been very strong with no issues up until recently. Fuel pressure is good at idle and WOT, compression is good across all cylinders. Exhaust consists of long tube headers, x-pipe, straight back into two single chamber race mufflers, no cats, and no airflow restrictions on either bank. There is a faint exhaust leak at the collector on bank 2 side that has started not long ago. It currently runs okay but just doesn't feel quite as strong as it used to and I can feel a misfire at idle. Heres the issue: I have a P0300 dtc and noticed LTFT between banks are skewed, 3.0% for B1 and 11.7% for B2. STFT reads -3.9% B1 vs 0.8% for B2. Is the small exhaust leak a big enough problem to cause this, or is there another possible cause?
It could be, depending on where it is. Do the numbers on that bank get better with rpms?
I haven't tried it, but have considered introducing propane at the leak source to see if it is sucking air in there. I haven't had one in a great spot to do that though and am not sure ho conclusive it is.
Would it be difficult to repair the leak to eliminate the possibility?
Is there a misfire counter that might help you determine which cylinder(s) may be acting up, and if they are on that bank? I don't love having a ltft number like that but it's not too bad really. It would just bother me, ha.
Jkmotorsports wrote: It currently runs okay but just doesn't feel quite as strong as it used to and I can feel a misfire at idle. Heres the issue: I have a P0300 dtc and noticed LTFT between banks are skewed, 3.0% for B1 and 11.7% for B2. STFT reads -3.9% B1 vs 0.8% for B2. Is the small exhaust leak a big enough problem to cause this, or is there another possible cause?
Regardless of the LT on B2 you are still in fuel control. Its possible that your misfire or misfires is on bank 2 pumping air causing that lean condition. Is it a dead miss at idle all the time or fishbite? Misfire monitor pids on the scan tool help at all? I would try to locate the misfire and correct that before chasing the minor lean condition.
Last edit: 3 years 1 month ago by Lowboybrian. Reason: Adding missed information.
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