For a long time after I bought this car used, the only thing wrong was the long crank-time during start -- which is explained by the bad cam sensor. The SES light was on but no one could read out the trouble codes. It would run fine other than that, good mileage and everything. Then about 2 years after I bought it -- about a year ago -- it started acting up when the engine got warm. I guess that would have something to do with loop status going to closed. The way the engine would act up would be to cut out briefly and repeatedly upon acceleration -- especially after I came back out after shopping to start it up again to drive home. It got worse and worse until if I made two stops in town, after the second stop, I could barely touch the accelerator without it cutting out a lot -- to the point that I could only get going about 10 to 15mph.
Of course, none of the mechanics wanted to touch the damn thing because they didn't have scanners that could read the odd-ball OBD1.5 on the 94-95 GM 3.8L engines. So that's why I got tunerpro: to read the trouble codes, which told me about the cam sensor.
Anyway, I gathered a bunch of screen shots of the graphs of rpm, air flow, O2 A, O2 B and fuel pulse timing under various conditions which appear below. A couple of things to note are 1) I think when I say "cool" it isn't actually "cold" -- in other words it might already have been running loop status closed, and 2) the sawtooth RPM and fuel signals were accompanied by the loop status oscillating between open and closed, with the downward slopes corresponding to open:
Ignition Swtich On:
Start:
Idle cool:
Gun it cool:
Idle cool after gun it:
Idle warm:
Gun it warm:
Idle warm after gun it:
Gradual gun warm:
Idle after gradual gun warm:
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