LTFT's...high

[Rhino79]

Well, we took my buddies truck out tonight and was scanning/logging some data trying to get it dialed in. The fuel trims were around +15-+25. So I added a little to the VE table, disabled the LTFT's, DFCO, and MAF, and Logged some STFT's, after 2 good logs and tweaking on the VE table I got the STFT's around +-5% across the table pretty much. So I figured I could re-enable everything and check out the LTFT's now since the VE table was off pretty good in some spots (as much as 20%in some areas). Well the LTFT's wandered back up to about the same spot as earlier! I scrolled over and checked the DTC's and there was a MAF Sensor Performance code (P0101 I believe). Do you guys think that is what is jacking the fuel trims up like that or do I just need to spend more time on the VE table?

[Rhino79]

Also should I re-enable the LT trims and leave the MAF disabled to check the trims?

[SSpdDmon]

You adjusted the VE table and then re-enabled the MAF? If you didn't tune the MAF table, then yes that is what's jacking the fuel trims back up. If the VE is closer to being right than the MAF, you could disable the MAF and run the truck off the VE with LTFTs ENABLED until you can get the MAF tuned. Hopefully the top end of the VE is right. You really need to do that with a WBO2 though.

[Rhino79]

Thanks, I should be getting a WBO2 next week, so then I can AutoVE it and the MAF. Thanks for the input I'll try checking the LTFT's with the MAF disabled and hopefully they will be a lot closer to normal.

[SSpdDmon]

Yeah...just make sure he stays in closed loop until you get it tuned (ie - keep his foot out of it).

[Rhino79]

Thanks SSpdDmon! Went out this afternoon and disabled MAF and Enables LTFT's and they were around -8~-12%, so after getting a good average in all the cells we could hit, I subtracted around 7%~10% and the fuel trims were within +.08~-3% for the most part! Well, then I re-enabled the MAF and scaled up the whole table by 5% just to see if the trims would act any better......NOPE, so I guess that the MAF is messed up? I just set it back up for MAFless and trims went to .08~-3% ! So until I get my wideband I told him not to hammer on it but he had to just once on the highway for about 3-4 seconds and it felt much better, the NBO2's were reading about 930 so it was a bit rich but then again I have the PE vs. RPM set to 12.3 until I can get the WBO2 on it. Thanks for the help, I really appreciate it, and also would like to say that after using the SEARCH button to look up some info on idle tuning and IAC counts, I was able to get the idle nailed down pretty close, I think the desired air flow is a bit high though because the throttle is "hanging" a bit on deceleration, but other than that, it's getting there!

[SSpdDmon]

N/P. If the throttle is hanging on decel, that's more than likely the throttle cracker and maybe partly due to the throttle follower. As for the MAF, it might be a good idea to clean the insides with a little quick dry electronics cleaner (found at local Autozone type store). Also, 5% might not be enough of a change to help much. My bolt-ons '02 Z28 needed 7% added to 5000+Hz to bring fueling in line. You'll see where you're really at once you get the WBO2 working...

[Rhino79]

Well in a few weeks I'm putting on a Victor Jr., 4bbl TB and some milled 243's to bump the compression up to about 11:1 and doing completley without the MAF and doing a AutoVE SD tune. I have just been trying to figure out over the last week why the LTFT's stayed at +25% no matter what I did and once I disabled the MAF, Trims fell in place good.

Oh and the Throttle cracker is zero'd out for the most part but the desired airflow is about 10.4 g/sec from 80*C and up, thats the way it was to begin with since he got this baseline tune (mailorder).

[VetPet]

After you've dialed in your VE table re-enabling the MAF puts you right back where you started from in the first place. You might as well leave the MAF disabled until you're ready to recalibrate the MAF. You should be able to do this as the PID needed to recalibrate the MAF has been added to the PID list in the scan tool. You did a pretty good job without having the use of a WB02 but you can further refine your VE table once you have a WB02. Keep us posted.

[Rhino79]

I think its pretty good and it's come a LONG way since a week ago. I have since been tuning on idle a bit, got the trottle blade set and IAC counts right, just trying to nail down some surging issues going from cruise to stop.