hooked it up to the diagnostic computer at parts store. Showed fault on #4 cylinder. Replaced coil, then plug, then wire. Still showed fault, still misfiring, still shaking like the engine was going to blow. Ended up at dealer, removed valve cover & the spring was broken. Dealer said "rare event".

Oh, & ran like crap when returned to us. Dealer had forgotten to hook back up the exhaust tube! Seems okay now....just some lifter noise which is new.