Rough acceleration in any gear 98 4.6L
My 1998 f-150 V8 Triton 4.6 runs rough only when accelerating - in any gear including park and neutral. It is sporadic too. I changed oil and filter, fuel filter, and all spark plugs. After changing the plugs I took it for a ride and the issue seemed to be solved. The next day it was back again. Just put in additive and filled tank. It ran perfect at first acceleration, then rough again on the second. Then smooth again and rough again. It seems to drive and idle perfectly normal. If you step on the gas quickly in park, the engine shakes a bit. If you accelerate slowly, there seems to be no issue. I can't figure this out. Any ideas?