Hello,
I have a 383 LT1 which I have converted over to run off of the 411 PCM (24x reluctor conversion, 8 coil packs, etc). By starting tune is a 2001 M6 LS1 Camaro, and I have been using a few other tables from a 01 5.7 Express Van. I have a small fuel trim split at idle, within 2-5%, however this is down from the baseline split which was around 20%. The LT1 Intake Manifold and Idle Air Circuit lead to poor cylinder balance, especially at idle with aftermarket camshafts. Due to this, I am fairly happy with the current idle fuel trim split. The biggest issue currently is that the fuel trims have a huge split on cost down. Ie 25mph+, 1500rpm+, and 0% throttle. During this condition, the fuel trim cell is 21, and the split is huge, often maxing out both banks in stft (+25/-25). You can see this in my attached log, around frames 445, 875, 1645, and 2200. What is the recommend approach to work this issue out?
See below for test performed:
Installed new spark plugs (NGK TR6)
Used an HEI spark tester to test each coil and plug wire
Switched coils from bank to bank
Switched injectors from bank to bank
Used a Noid light to test the Injector harness
Tested for voltage, ground, low reference, and coil control signal at each coil.
Double checked, using a digital volt meter, the PCM continuity for the coils, injectors, and O2 sensors.
Switched in the stock O2 sensors
Performed a compression test on each cylinder
Tested fuel pressure regulator for leaks and for proper pressure at vacuum
Ohmed each spark plug wire
Checked for vaccum leaks / exhaust leaks using brake cleaner and propane
Installed new exhaust clamps at the header collectors, along with exhaust sealer
None of the above has helped resolve the situation.
Thank you for the help,
Jahajazz