Quote Originally Posted by rudder2fly View Post
What does BLM represent? I have a 1989 Chev K1500 350 with a 1227747 ASDU computer. I have both the TunerPro Rt program and the WIN ALDL program. I am trying to find out why my engine will not run correctly when the alternator is charging? I can unplug the single signal wire to the alternator and the engine will smooth out. When the wire is plugged in the motor will go down when accelerating and continues to surge. The tuner program shows a fault [in red] 155 BLM long term fuel trim? When running at less than 12V the number is 128 BLM. If I stay in the throttle long enough the INT fuel trim will go red also? Any help will be appreciated. Thanks G.S.
All good advice above...

But your issue is not the altenator or charging system. You just found a way to make BLM/Long Term Fuel Trim come to the number you wanted. It's probably loosing enough voltage to go Open Loop, so no O2 sensor feedback? Which would always be 128.

You have TunerPro RT, so no reason to do data logs with ancient technology, WinALDL is like data in brale... get your ADX file and learn to data log with TunerPro. I know it's a little harder to get going but the results are well worth it and we can take a look at what your problem is.



155 BLM is adding a lot of fuel. One thing this ECM can not do and does not know, it expects to be correct is fuel pressure. So you will need to check fuel pressure as well.

Is the motor stock? Any mods done please list them.