Thanks so much for the info!!!
I see that pulling the plugs is no easy task in itself
Is there no other way to determine which is Cyl 3? It would be so much nicer to be able to target the problem cyl and look at the plug, coil, etc and go from there.
Originally Posted by
Padgett
P0303 is cyl 3 misfire & raises the question of "which is cyl 3 ?" since Merc uses odd cyl numbering.
Once that is sorted there are three things that usually cause a 303 (which is basically that the engine slows down when #3 is supposed to fire):
1) mechanical - e.g. a burned valve - rarely heals
2) fuel - clogged injector (high engine speed & high load)
3) bad secondary ignition (low engine speed, moderate load) (coil, wires, spark plug)
I'd probably pull the spark plugs and take a look first.
ps if misfiring I use an IR temp gun to determine which - the bad cyl will have a cooler exhaust manifold.