Odd problem, could be MAF related but I'm looking for ideas

[thunderstruck507]

My car has been temperamental lately. For a month or so the shifts have been getting noticeably sloppier ( I was thinking tranny was going out). Cleaning the MAF didn't help so I wrote that off.

The other day I added a 3" pvc tube to my intake ducting to get the filter down low instead of right behind the radiator to try to get cooler air (temps were 120+ and now they are 90-104). I also found a local place to get 93 octane instead of 91 or 92. I was getting 2-3 kr before so I thought it might help. At first no, but now I rarely get any kr...still 2 every so often at wot.

Nothing was noticed at first but then a couple days later the car began running noticeably stronger, shifts firmed up, WOT shift points raised, downshifts became more responsive, and the car was all around better. I noticed a change in MAF readings from 36-37 lbs/min to 40 lbs/min.

Now it jumps between the 2 randomly. I can't find anyone who has a maf I can borrow right now, so I'm curious if anyone might have some ideas on other things to look at or look for.

Another point of interest is rarely the car becomes a complete dog. Upshifts to 3rd as fast as it can once the car is rolling and then refuses to accelerate or downshift. This happens for a few minutes regardless of whether the engine is turned off and then back on or not. After a few minutes it goes away...usually for weeks at a time.

Thanks for any and all advice or ideas.

[joecar]

If the PCM calculates cylinder airmass too low then it may be commanding low line pressure (the PCM's computation/lookup chain is airmass -> torque -> pressure).

If you can't sanity check the MAF, try running in SD (MAF-less) and see what it does (log DYNCYLAIR, DYNAIR, TRQENG).


The immediate upshifts and no downshifts are indications of bad TP and/or VSS sensors...

check your engine ground connections also.

[thunderstruck507]

the other day the maf was accidently left unplugged and the car would not start at all for several tries then I finally got it started and it idled terrible and would barely stay running before it finally tossed a MAF circuit low code

not sure if that's relevant, I'm a noob to the whole tuning thing but I do know I've heard of people unplugging mafs for troubleshooting and never mentioning it causing the car to not start or run

[thunderstruck507]

I borrowed a MAF from a truck someone dropped off at my dad's shop today.

I put it on and went for a drive and the car runs good, and feels like it pulls hard even though apparently the fuel I got today was junk because I creeped 30% into low octane table. But even still I can feel a decent SOTP difference than this morning when I was running on good 93 octane fuel and 100% in the high octane table.

Sad part is before this I went out of town and got on it once, something happened going into 3rd gear it was like all line pressure was lost as the rpms jumped from 5k to 6k almost instantly, I got out of it as quick as possible. So I think I smoked the clutches pretty good :(

Did notice on the old MAF there was some kinda liquid coming from the black electronics casing. I'm gonna drive some more later and see if it stays running well or dumps back into crap mode like it does with my MAF.

[joecar]

I'd say the MAF is damaged...

If you released the throttle quick, you maybe may be ok... check fluid condition.

Remember this: stock 4L60E is good for about 400 ftlb... any slippage you see going into 3rd is a sign that the 3/4 clutch pack is on its way out.

Post tune file.

[thunderstruck507]

The fluid is still a nice red color, has a faint scorched smell and feels a little different to the touch than normal. We're going to drop the pan and have a look, replace the filter, and replace the pressure control solenoid. Also look for loose grounds and such.

I am attaching my current tune file and a short log that should contain a couple WOT runs and a longer one that has some slow cruising, easing into throttle, and wot all mixed together.

It's been very hot and humid here (100degrees or so with 60%+ humidity)

Thanks for your time, it is much appreciated.