The gapping might not be as specified. I would try replacing them first to see if it solves the problem.
Have the compression tested if changing the plugs does not help.
Coils can be tested for resistance but if it is misfiring on all cylinders, the likelyood of all coils failing at the same time is almost zero.
Apart from compression, check the fuel pressure and exhaust system.
Monday, April 4th, 2011 AT 8:23 PM