I found the yellow sensor wire that goes from the MAF sensor to the PCM wasn't clean when I used my Ohm meter, it showed about 1.71. I ran a new wire along the same route and spliced it into the existing connectors. The new test drive was markedly better in acceleration and speed. However, after clearing the code, it still showed ""PO102, Mass of Volume Air Flow A, Circuit Low."

I grabbed an older laptop in great condition with XP on it, so I could run the GM program to flash the PCM, I'm loading XP Professional on it with Service Pack 3 so it should run it properly, and I'll "flash" the junkyard PCM first to my daughter's VIN and see if that fixes the issue. Sound Like a good plan?

 

Finished (though I had to go to a shop with a Tech 2 and basically rent it with the mechanic).

Everything is factory spec, and it idles and revs without issue. No trouble codes. Everything is within spec. when we looked over all the info in his Tech 2 readings.

When driving (though markedly better and gets up to highway speed great), still it seems the engine, as it is accelerating: feels that it either adjusts the fuel/spark a bit, or the transmission shifts prematurely into a higher gear or something (that's the only way I can describe it). It's weird to feel the car do something without driver input. Whatever it is is keeps the car from continuing its acceleration for a few seconds. If I give it throttle during the event, it downshifts and accelerates great through the issue. If I don't alter the accelerator, and keep it steady during the event, it waits a few seconds and then shifts to overdrive and feels normal.

Since I changed the fluid and filter when I first was alerted of the issue by my daughter during my maintenance work, and the old fluid was discolored (aged) and there was no metal dust or filings on the magnet, I'm wondering if I just need to allow her to drive it and change the fluid again in a few days and see if it flushes more of the old fluid that was trapped inside the torque converter?

 

I'd replace the modulator before suspecting torque converter.

 

I didn't really think torque converter problems, just the fact that there is old trans fluid in the converter that wasn't changed out when I did the fluid and filter flush. I have always heard that new fluid in a high mileage trans could dissolve and release some old trans fluid shellac that has built up and cause some issues with the shifting in the pressure plate orifices. Just a thought.

Also though, there is the vacuum powered trans modulator that might be a issue? I have only read hard shifting and lack of shifting as an issue on those failing.

 

Yes, and it is adjustable. I replaced mine for whatever reason, possibly the same issue you are having, but it was inexspensive at that time. I still have my 96 DD.

 

So I pulled the vacuum modulator and it was certainly bad as the piston was lose and the replacement one had a tight piston. Although the car shifted better in accelerating, it still had the moments of 'drag' or whatever and I had to mash the accelerator to push through it.

Looks like the throttle valve -the part the modulator pushes against inside the transmission- is also a culprit. What are the odds they both go bad huh? Anyway, the test procedure requires a few tools I don't have (trans pressure gauge, an adapter piece, and a Vacuum Gaga Pump combo). Looks like the transmission shop might be my only option.

Thanks. The journey continues, whether I want it to or not, haha.

 

The transmission shop checked it and stated, "the transmission is working within spec and the delay in acceleration was an engine issue, though no code is being thrown. You can come get the car when you can."

Back to old "Square One".

 

PROBLEM SOLVED
So my friend has some awesome equipment to test Hz and other sensor feedback and we looked at the Knock Sensor and the O2 Sensors (much more sensitive than mine as well as had the exact ranges of signal that should be expected). The Knock Sensor and the O2 Sensors both looked slightly out of spec, enough to do a test drive with first the Knock Sensor disconnected and then a drive with both the Knock Sensor as well as the upstream O2 Sensor disconnected.

With the Knock Sensor disconnected the drag or delay in acceleration under load was gone, though it wasn't completely smooth. With both disconnected, it drove really well and there was no drag or delay or alteration of power during driving. I replaced both the Knock Sensor as well as the upstream O2 Sensor and tested the car again. It drives as it should.

So, in the end, the car had these issues:
1) the #1 cylinder had a head gasket leak, fixed with head gaskets replaced
2) the MAF sensor was sending inaccurate info and had a damaged wire, replaced
3) the vacuum Transmission Modulator was broken, replaced
4) the upstream O2 Sensor was not within spec, replaced
5) the Knock Sensor was sending wildly inaccurate info, replaced

Interestingly, only item #2 above was determined by the PCM to be in error and would throw a Service Engine Soon light or throw a code, the PCM was silent on the other errors. I guess a '97 GM PCM was not very sophisticated.

Anyway, thanks for your help!!!

 

Sweet!

 

Yeah, but that sweet was a bi*ch to make and stayed waaaayyyyyy too long in the oven, hahaha!