1999 Rodeo/Passport strange transmission issue

I have a 1999 Isuzu Rodeo LS, 2WD/V6/Automatic (same vehicle as a Honda
Passport, so I have crossposted to both Isuzu and Honda) that has a
strange transmission issue. I want to know if anyone has ever seen
anything like this, or has any suggestions.

Every so often, with absolutely no warning, frequency, or anything
causing it, the Rodeo will start shifting very rough. It will buck when
switching gears, either upshifting or downshifting. Most time shutting
down the Rodeo and leaving it for about 5 minutes will cause it to
start working normally again. Sometimes the issue will happen when I
first start driving it, other times it happens while I'm driving it - I
may be driving along fine, come to a stoplight, and when I start going
again it will start shifting rough.

It has about 91,000 miles on it. I just replaced the transmission
filter and fluid and that didn't make a difference. Right now it's
running fine, so I'm not about to take it to a repair shop until it
starts happening again.

The strangest thing is that this also happened with a car I had
previously (2000 Saturn LS2). The transmission shop couldn't find
anything wrong with the transmission, but suggested I replace the
Throttle Position Sensor. That is only sold with the throttle body
($300+) so I ended up living with the issue and trading it in before it
was fixed, so I don't know if that was the cause of the problem in the
Saturn or not.

Thanks for any and all suggestions,
Jake Williams
Madison, Alabama

Thanks for that advice. Were you getting a check engine light or
anything like that to lead you to hook up to the OBDII? I have not
tried that yet since I've never gotten a check engine light. I will
have to do that next time the problem surfaces to see if it reads
anything.

Thanks,
Jake