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Old 04-04-2008, 10:54 AM   #663 (permalink)
TurboBob
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Join Date: Jan 2003
Location: Near Detroit
Drives: 86 GN 91 RT/TT
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Default Re: Lean Misfires at 2700-2800 rpm

Quote:
Originally Posted by badass3000 View Post
all of last year I was too thinking something electrical, but after replacing every unit/plug/sensor that could be related I have to start looking somewhere else.

Bob, are you thinking that even though we have tried known good ECU's, that our ECUs are still faulty -or- perhaps receaving an improper signal causing faulty results?
I don't think they are 'faulty' or this would be fixable by swapping ECU's I thiink its related to the calibration on the stock vehicle. The stock vehicle was most likely programmed to comply with emissions regs below 2800 - 3000 and not above. Thus the abrupt switch. So below 2800, EGR is maxxed, and the tuning/calibration is optimized to run cleanly. This may make the car sensitive to old ignition coils, cold plugs, etc.

I have watched the scanmaster during this transition point and spark advance does not appear to change, but the datastream may not be fully accurate.......

running open loop thru this point seems to help. I just wonder if part of the transition is due to weak spark from low ignition dwell...

Bob
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