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Which is it hesitation of slipping

1994 olds 88 royale with 3.8 sometimes hesitates or “bumps” when accelerating. sometimes it seems like the tranny is slipping, but other times it seems to feel like poor firing or slight misfire with hesitation. when at highway speeds of +50 it runs fine but occasionally bumps or seems sluggish if i rapid accelerate or speed up to pass. do i have a tranny problem or poor performance or emmisions problem thanks for the help and Click n Clack are the best

When was the last time spark plugs were replaced? This could be a motor that needs new plugs and filters which is essentially a “tune up”. It could also be your transmission is slipping and the 1st thing to check is the level of your transmission fluid. A trans that is low on fluid could cause similar symptoms.

A more complicated problem could be the lock up torque converter is locking and unlocking improperly. Could be low on fluid, or the electronics controlling the transmission might be out of whack. A mechanic can scan for emission codes and transmission codes to aid in the diagnosis.

If the transmission was recently serviced, and that service was a “flush” I’d lean toward a transmission problem. Refilling with improper fluid could cause symptoms and a poorly done flush can move dirt from the transmission pan back up into the workings of the transmission.

Perhaps some more info on recent maintenance, or lack of maintenance, on the car can help narrow down the possibles into what is most likely the problem.