Terry,
Thanks for the info. I should have a scope, but wouldn't use it 99% of the time in what I do and I won't admit that I work on too many cars. Typically it's my car that becomes the headache and all the others are straight forward.
The hiccup has changed and given me more info to go on.
Originally it would happen on the highway typically in fourth gear at steady rpm of about 2k. I'd feel a small quick pulse in the car, similar to running over a difference in pavement. Except without the suspension travel. At that same time the tach would quickly jump approximately 1k rpm and return down to 2k as if nothing had occurred. Usually happening once or twice in say a 20 mile drive. Infrequently it would happen 15 or so times in a row, this was very infrequent though. A few times I saw the behavior in 1st, 2nd or 3rd gears as well.
Without ever really diagnosing, I blamed it on probably an input clutch piston seal and called it a transmission issue. I built a complete transmission from other parts and swapped it into the car. Had the incorrect reluctor on the diff from an old spoof for 3.29's and once that was corrected all seemed good with the trans for a moment. Then I realized the problem hadn't left and was occuring more often. More often being a good thing in my eyes. Intermittants are tough to find.
Using HPT I scanned, saw where the rpm spiked once on the scan and dropped down about 500 rpm suddenly in another area (as you say..scanners can be slow). MAF and TPS appeared steady and not moving during the spike. Being that I have tested spare parts laying around,
I programmed up a new pcm and gave it a try. No change
I then thought about how flakey out crank sensors are and swapped it out, no change
Off the wall, but maybe an ICM, swapped it and the coils, no change
During a test drive, pulled over, killed it and unplugged the maf. Car fired up nicely and now appears to not be spiking up, only dropping down. Pulled over again and cycled the ignition. At this point the SES pops on for the MAF being unplugged and I test one more time. Still dropping rpm although it seems more often and only drops, not spikes. In more gears at more speeds. Typically though it appears to be in the throttle, where it would be most apparent. Plugged maf back in and about the same behavior.
HPT would display misfires etc current and history. It's not seeing any according to the pcm. Typically if I have a mis on a car, it's seconds to spot it with the scanner.
Tonight the plan is...back to basics: Aiming to look over the plug wires, swap a tps and probably the maf as well. Thinking I may as well swap out the map, but there's no logical reason that I can think of.
