Working on a tune for a stock LM7 with long tubes, a Velocity intake manifold and a less than-ideal intake tube setup in a 48 Chevy pickup. The issue I'm having is an idle stumble that I can see is being caused by the idle advance table, but I don't know what my next steps are. You'll see that the table will add up to 12 degrees and then it seems like the computer tries to correct something. My only guess is the airflow is off because of the different setup
A few notes:
-Pretty new to tuning still, I went to The Tuning School a few months ago, and this is maybe my second factory ecu I'm working with, all my other experience is with Holley Terminator/Dominators
-I have the MAF disabled because the sharp angles in the intake setup.
-I didn't realize until after my initial idle and part throttle tuning that the idle speed and some injector settings were previously changed, so I set them all back to the factory form a stock tune
-I'm starting over now, and the idle stumble seems to be more pronounced after the engine has been warmed up, and it'll even die sometimes. It made getting the idle fueling down difficult but it's pretty close now.
Happy to give any other necessary information and I hope this isn't the wrong forum! Thanks
-I've reverted back to the tune I had before I made the injector changes and did some logging.
-I'm noticing that the momentary idle stumble is nonexistent until the IATs get up over 120ish degrees. After that point the LTFTs start adding a ton of fuel and the spark starts to get bumped to 30* to correct the drop in idle(?). I used a shop fan to cool the IATs and saw the LTFTs drop back 0-3%.
-I checked the intake tube temp with a thermal laser, and it's showing only about 110*, which was about 15* off from what the IAT was showing that that particular time. Is the MAF temp sensor off, is there a calibration to do?
Scanner is stills showing that the correction is coming from the Idle Advance table, I'm just still at a wall on what to adjust or correct.
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