2001 ZX3 Engine Surge ....
First time poster here.
2001 ZX3, automatic, high mileage at 142K. Car has begun to surge while driving at slow or higher speeds. At slow speeds sometimes RPM's will jump significantly up and down, then level off. At high speeds it will ramp up at about 3000 on highway, but will jump up and down about 250 RPM's softly.
When car reaches a stop, it will sometimes idle high wanting to move forward if brake not pressed, and at other times it will idle correctly. This is an inconsistent pattern.
Sometimes car will idle higher than normal when car is in park on in neutral as well, again inconsistent occurrences.
No engine light on, not other noticeable issues. Car excelerates as it should without hesitation.
Thoughts? I know you've probably seen this many times, but any thoughts would be well appreciated before I just surrender it over to a mechanic without having a general idea of some possibilities.