4.6 rough idle
 

friend has 4.6 in Mercury Marquis. Had cracked intake manifold,which has now been replaced. Cylinder 3 and 4 still seem to be missing,compression 150 plus in each,has spark. Original alot of water coming from muffler though maybe head gasket leaking so he drained coolant,no evidence of coolant in cylinders. Anyone got suggestions. Guy is a retired Ford mechanic, retired early 90s not familar w this engines internals told him I'd put post here.Thanks in advance. Car does run but rough,

what year is the motor??? water out the muffler is not a problem.thats the catlytic converter doing its job.

1998 car and engine,sorry I forgot that

i think 98 marquis has c.o.p coil on plug. i have a 96 crown vic that has the coil packs, so im not to familiar with the c.o.p. im sure others can help diagnose. how are the plugs? fuel filter? tune up related items???

cops appear to be working as when doing compression check you could see nice blue spark jumping across the electrode.