The car runs fine but wen i go up between 70 -80 mph is very shaky

Question

The coils check out fine I also swap the spark plugs there is no oil in the spark plugs shaft , what can it be ??????

Answer 1

When there a misfire condition with the ignition system is either under load, or at idle and the CK ENG LT will set, At 70 to 80 and the vehicle gets shakey you may have to check the drive shaft center bushing