need Some help with LT1 MAF issue

[Fastmax32168]

My 94 Corvette has developed an issue which leaves me scratching my head. When you first start it, before the O2 sensors kick in, everything appears normal. As soon as it goes into closed loop, it begins to add in fuel the longer it runs, until the BLMs max out at 160 after a cell has had enough hits. You can tell it is pig rich by the way it runs and the smell of the exhaust, even though the ECM still thinks it is lean. Now....if I unplug the MAF and put it into speed density mode it does not do this. It runs as normal. The BLMs stay where they should. I have replaced the MAF, as the old one had some corrosion on it, however it has made no difference. . I have searched for vacuum leaks and found none. Suggestions?
Thanks,
Roy

[steveo]

lets see a datalog of the issue occuring. there's a lot of information we don't have such as what your maf airflow is reading, as well as what conditions this occurs in, maybe we can eliminate some possibilities at least

a large air leak between the maf and the intake manifold would be the most common cause if speed density seems to fix it, but that doesn't line up with the fact that you say it runs normally until it hits closed loop. also switching to speed density might be enrichening things enough where it's becoming a band-aid for something.

on a car made in 1994, every wire and also every rubber thing can't be trusted. for example how is your maf and o2 wiring? gm made those wires really thin. you could have one or more that's morphed into a resistor over time.

one cause people overlook for a perceived over-enrichment condition caused by high trims like this - you could have a non-firing cylinder. that cylinder acts like an oxygen pump and floods the o2 sensors, making them think things are quite lean, so they dump a lot more fuel, in turn making the remaining cylinders quite rich. you'd usually be able to tell that as trims would be quite different per-bank, though, and reading plugs should be a smoking gun if it's been running like this for a while.

[LeMarky Dissod]

Check for air leaks between the MAF sensor and the O2 sensors, intake and/or exhaust manifold leaks being the most likely culprits … and pretty much everything steveo said.
H2Opump wiring is also notorious for being made of wires that were too thin & brittle 25 years ago.

[Fastmax32168]

Thanks for the responses. This problem isn't exactly what I thought it was, it was adding fuel everywhere before I replaced the MAF and I thought that problem was back but it appears to be mainly at idle now, and worse on the right bank. I sure would like some of you that are smarter than I am to have a look at this file though since it is all over the place. This is actually my first EE hack file here, I have always used tunercat, but there certainly seems to be a lot more info in this program. A little history here, I have had this car for 15 years, it has a very healthy 383 in it that will propel it to high 11s at our local track. I left it sit with little use for a few years and it was running badly, so I cleaned all the njectors installed a new fuel pump and filter, opti, coil, plugs, wires, and maf sensor to freshen it up. I have new O2s here but haven't put them in yet. Other than the poor idle, it sounds and runs decent driving it around, but as you can see from the file, the tune seems all over the place. I looked hard for air leaks either before combustion and afterwards and really cant find any. Keeping in mind that this same tune would log good a few years ago, on the exact some motor, is it possible that changing around all of these components has affected it to the point where I need to start over again, or has something else gone haywire? Any input here is appreciated. Thanks
Update: I cant get the eedata file to upload and attach. It keeps saying invalid file. I dunno

[kur4o]

You can zip the logs and than try to upload.

[Fastmax32168]

Thanks, let me know if you can open it now