Appreciate advice.
1999 s80 non turbo 2.9L

My car started up OK but when I pulled away it felt as if there was a cyl misfiring.

I pulled up an error code P0304 = Cyl #4 misfire detected.
I had replaced all plugs 4 weeks ago. Car ran fine until today.
Could this be a faulty plug or failing coil - how do I check the coil.
or what ever else it could be.
BTW which is Cyl.1 - Near the time belt cover or the other side near the filter

Look forward to your advice..

Mort

Cylinder 1 is closest to the front of the engine/timing belt. For a quick down and dirty diagnosis pop the coil cover off, inspect your wiring to make sure that you did not pinch a wire when you put your plugs in last time. If that all looks could then go ahead and swap the coils from cylinder #4 with another cylinder and put it back together. While in there you can also pull that number 4 plug and see if there is a cracked porcelain or anything else that may cause your problem. Did you use a quality plug or some kind of aftermarket b.s. wonder plug? Fire it back up and see if it still misses, if it does still miss then pull the code and see which cylinder is missing. If it is still in hole number 4 then you need to consider things like a faulty plug or injector if it has moved with the coil then you need a coil to start and if it is a coil then you may have more of them in your future.

mark

Thanks, Marc, I replaced the defective ignition coil.
Mort