RPM'* fluctuating under load
Most prominent at highway speeds, the RPM'* in my '97 Bone SE fluctuates between 2500 and 3000 when there is a load on the car such as climbing any type of grade (although there is fluctuation at time on the flat also). I recently had the 4T60E in it gone through as it had burned up. Also recently replaced the plastic upper intake manifold and spark plugs, water pump & hoses, alternator and battery, serpentine tensioner and belt. I seem to recall fluctuation prior to the trans going out (funny story I'll tell later) but there was too much other activity going on to isolate it.
Anyone seen RPM fluctuations like this? I'm wondering if it going to get worse, and am looking at ECM as the cause. Does not fluctuate at idle, so does not appear to be idle controller.