96 Z28 LT1/383. has been tuned and running good. the scanner I have shows my timing at idle at -24, how can this be possible, another friend checked with his and it showed the same thing, should't it be at 24 not -24. next question the LTFT shows on bank 1 +17% and on bank two +4%, how can you correct this using TC program, I thought you could only program for both sides at the same time, can you tune for just one side fuel trim, still no codes

 

The timing is "advanced" 24-degrees, which means the spark is occurring 24-degrees BEFORE (= -24-degrees, referenced to) TDC. Some scanners drop the negative sign. Don't worry..... its not firing 24-degrees AFTER TDC.

If your BLM's are "split" that badly, figure out why they are split. Don't try and correct them until they are closer to being equal. An elevated long term fuel trim like you have on the left side may be the result of an exhaust leak before the O2 sensor, or misfires on that bank. They both create a "false" lean condition that causes the PCM to add fuel the engine doesn't need on that bank. Or, possibly a faulty O2 sensor or faulty harness extension. Swap the O2 sensors side-to-side, and see if the elevated BLM switches to the right side. That would indicate a faulty sensor.

Which cells are you seeing the BLM's you quoted? If they are only on the idle cell (16) it may be due to idle air distribution problems, or reversion from a big cam.

 

I'll check what you wrote and get to you later this week, that makes good sense to me, thanks alot

 

Injuneer rulz