After scanning today i agree. The numbers were night and day between open and cloed loop. Usually it is like boader line, today it was night and day. I am waiting for Ryan to get back ahold of me with his thoughts. I would like to get this fixed and hit the track before the end of the month.

Terry,

You have your scan titles reversed...what you titled "open loop" is actually closed, and vice-versa.

(I'll post some thoughts after Terry fixes the titles )

yeah i saw that also

LOL fixed.

My IPW'* are at 18 so they are fine. Once in a while i do see them hit 22, which is maxed out but it is literally once in about 50 runs or something crazy like that.

I do note in your scans that, in open loop, the MAF readings vs. rpm follow a nice, smooth upward progression (as they should), whereas with your closed loop scan the MAF readings vs. rpm are all over the place.

This has me thinking your PCM programming is somehow corrupted...didn't you say you have another '95 L36 PCM you could swap in and test?

(Although how your PCM may have gotten corrupted I don't know...crossed wires in the harness?)

That is funny you said that lol. When i sent Ryan the scans i sent him a message saying i saw almost the same thing. The car is fine in open and the parameters are normal. In closed they are all over the place. And i got random readings. Look at where i have ? marks in the scan. Plus i saw as much as 29 degrees of timing in 1 scan. I saw random stuff, like where the iat temp went from like 54 to 90 and back to 54 between like 3 frames. Just wacked stuff.


I am going to switch out that pcm.

PS---- something that maybe related but maybe not is.... My fan override doesnt work anymore. The fans just come on when they want and go off when they want lol. Mostly they just come on when the key is on and stay on. I can turn the override switch on and off and the fans stay on. Just figure i would throw that out there

Ya know, looking at your closed loop scan, something struck me...

There is some debate on the tuner forums as to how the VE table in the PCM is used in a MAF-enabled engine.

There is one camp that says the VE table and MAF data are somehow "blended together" by the PCM at rpm below 4000, after which MAF takes over entirely.

The other camp says that VE table is simply a "backup system" in case of MAF sensor failure.

I gravitate toward the second camp because I have done targeted experiments in my OBDII '98 L36 where I screwed around with the VE table on purpose to try to cause a "reaction" in a MAF-tuned tune...and I could get none.

The first camp I always thought of as "urban legend" believers or perhaps "holdovers" from the LT1-edit days; however, perhaps indeed your '95, OBDI (-ish) PCM does do some kind of VE table / MAF blending once in closed loop. I say this because I note that in your closed loop scan, the MAF vs. rpm "discontinuity" I see occurs at just about 4000 rpm.

What this has me thinking is that perhaps your PCM'* VE table just cannot deal with your cam, and simply has to be re-programmed. Why this would cause screwy MAF readings I don't know...and unfortunately, this is where my usefulness ends, 'cause I have no experience programming an OBDI system.

Well Andrew, i thank you alot for that input. I have done so many scans and sent them to just about every company or person i could think of and not 1 person could give me insight on it. I mean truthfully what you are saying is a little above my knowledge of tuning but it does seem to make sense. I am going to pass it on to ryan and get his thoughts since he has insight on obd 1 tuning.