Hey All,
I have a customer with a 1978 TA with a 6.0 G8 engine with the LS3 heads and intake. The cam is a 226/232 114 and it is a TKO 5 speed trans.
The controller, harness and accel pedal are all the kit from GM for the 376/480 engine. They used the supplied MAF and mount and it is in a 4" tube with about 6" of straight tubing before and after the sensor.
Everything is great as far as start up, idle, cruise and even WOT power. The issue is that 75% of the time it will go into a reduced power mode and only happens under heavy load (90-100% throttle approx) and run up into the higher RPM's. After the run and while it is barely idling in the limp mode, you check for DTC's and both the P1516 and P2101 are stored. Clear the codes while it is running and it goes back to running normal instantly.
Initially I opened up all the airflow diagnostic tables and still would go into a limp mode. I then tuned off the P1516 and P2101 codes in the DTC tables (both to SES Enable Off and Error Mode 3-No Error Reported) and on the first dyno run with these settings, no codes and runs well after. Did a second run a short time later with no ECM changes and again goes into limp mode.
I then had a known good TB off of a 2007 Z06 and did two back to back dyno runs, no codes and runs well, for now. After a long drive with no WOT, still good to go. One WOT run and back into limp mode. The limp mode and codes always happen as the accel pedal is released, not under load.
My customer is going to try another TB just for trying sake. I have done some reading and searching here and some folks have the same issue with no fixes that I can find.
Here is the current tune with the codes off as well as a run where the code set (Dyno4) and one where it did not (Dyno3).
Let me know what y'all think as this is a new one for me.
Thanks.
Mike Norris