Multiple Misfire Help

Plug wires are original. It is misfiring on all cylinders pulling the code P300. I would assume that means plugged cats then because it isn't happening to one cylinder in particular?

I would deff say start by looking at ur plug wires, we had a car in here yesterday throwing the samy code, multi misfire it had 2 bad plug wires, gave it a tune up good as new... just my 2 cents....

i have the same code coming from my 2001 6.0L, ive sprayed the wires and coils with water at night, didnt see anything, didnt change anything, it has the original cats on it, kinda hard to rod out with the factory bends in there, i am changing plugs and wires this weekend, see if that helps, if not, gotta get rid of the cats somehow.. any more suggestions? it doesnt miss any, runs great, just flashes the code multiple cylender misfire... thanks for the help guys!

mine had p0300 and 2,4,6,8 had mor than 1000 misfires on each.took the kitties out and now she screams.take your rear 02 sensors out and see if the amount of exhaust coming out of the bungs are the same.if one is plugged youll know.or an infrared temp gun on each cat.my drivers side cat(good) was 180ish and my passenger (bad) was 365 degress.

thanks ill take a temp gun to the cats and see if thats causing the codes,,

I got the eBay long tune headers. They came with a Y pipe and deleted the cats. 02 sensors bolted right up. She screams now!

Sorry for not getting back to this, I have been very busy. The truck has apparently fixed itself; it was still misfiring after we put the cap and rotor on and my buddy didn't want to throw any more time or money at it so he just left it. Well some time in the last two weeks it fixed itself. No more misfires, no more lack of power, it runs perfect. Time to sell it!