92 olds 88 hesitation

engine runs smooth as silk accelerating,decelerating,and idle when parked,but runs rough when trying to maintain steady speed,especially when engine warmed up.have changed fuel filter,plugs. also ran feul inj cleaner and dry gas.tried premium gas.car has 106k miles.car will jerk back and forth when steady speed on highway.thanks for input.

Anybody with a solution to this problem? I have the same issue with my car. I find that it is worse when the AC is on.

Check the fuel pressure under these conditions, use a gage with a long hose taped to the w/s. If ok this could be caused by a std misfire condition , a wire, a coil, lean mixture from a weak o2 sensor. Forget the premium waste of money. A full scan may point to the problem more readily than guess work, but if it is a misfire some info would show, fuel trims for example. 41-47psi is the normal fp. BTW in the future start a new thread, this one is too old.