Quick_Trans_Am

iTrader: (2)

Hey all, I'm fairly inexperienced with tuning, and I'm having an issue with my vehicle. Every diagnosis I've tried has led to a dead end. The car seems to be very hesitant when I hit the gas in closed loop operation, to the point that if I hammer the throttle from a dead stop it will cause it to buck and kick, spit and sputter, and stall every time I try to burn some rubber, or if I just want to give it more than 5% throttle it seems. This issue seems to be consistent in the 14-1800 RPM range, and I can't for the life of me figure it out. That being the case, I did three data logs to see if it could shed some light on the situation, the first being the factory prom, the second being a custom one I had made for the car, and the third being the custom bin with the BLM locked at 128.

So, now I ask, is someone here willing to take a look at them and let me know if they see anything that looks out of the ordinary?

The car is running a 730 ecm and AUJP code.
Thanks to anyone that can shed some light on this frustrating issue.

P.S. The logs are in .CSV format. I can get a .txt I believe if anyone wants it in that format.

RBob

iTrader: (1)

I looked at the first log with the stock calibration. The O2 is going very lean at times. Look at the area starting with sample # 975. About 6% TPS, 1700 RPM, 45 KPa MAP. The O2 drops to double digits, way lean.

If the fuel delivery (pressure/volume) is OK then I'd say need to work on the VE tables.

Also note that the ECM is locking the INT at 128 for some reason. Appears to be in closed loop with commanded AFR of 14.73. The EGR DC% is 100, which is full on. If there isn't an EGR present this will cause the AFR to go lean.

RBob.

Quick_Trans_Am

iTrader: (2)

Rbob, thanks for responding to my post. I had never given the EGR much thought, but since you mention it, the cylinder heads do not have EGR passages. Is there a way to go about eliminating that from the calibration?

RBob

iTrader: (1)

Set the enable temperature threshold high:

L82B0: FCB 46 ; IF MAT < 30 DEG C DISABLE EGR

Won't turn on, EGR diagnostics won't run. Won't lean the engine, won't add spark timing.

RBob.

Quick_Trans_Am

iTrader: (2)

I found it, thanks very much! I'll get a new chip burned and see how that helps this issue. I see a table here for the EGR duty cycle as well. Would it be as effective to turn the duty cycle to 0% across the board?