Within the last couple of weeks I've been working on getting rid of a CEL on 1 of my work trucks, a 2004 Dodge Ram 1500 with 5.7 hemi..

I had a bad 02 sensor, bank 1 sensor 2, which has been replaced.

I installed new spark plugs & coil packs which judging by the looks of the old ones, haven't been replaced in a very long time. It runs great, however, when you first start it up in morning, you feel it run a little rough/misfire, then goes away while in use, runs great. Once you park & shut it off for a while and the start it up again, it repeats the initial start cycle.

I was able to get my hands on a scanner, innova 3040e. The only code popping up is P0300 Random/multiple cylinder misfire.

Unfortunately, this scanner doesn't show which cylinder(s) has the misfire(s)

I would like to get some recommendations on how to proceed to get rid of this problem.

 

What plugs did you put in?

 

Champion copper plus 570

 

Multiple cylinder misfires are rarely caused by plugs or coils, since it's rare for two or more of these to fail. Look for a more central culprit, like the cam or crank sensors. Mopar only, if you replace.

 

Those are the correct ones, sometimes people put in rare earth ones and get that code. You might get more info out of a $15 bluetooth obd2 reader and a phone app. The spark plug wires (they go to the other side for exhaust firing) could be cross firing, if they're originals - not sure it throws a code on that or not.

Sometimes you can spot leaking sparkplug wires in the dark with the hood open and engine running. Try spraying it down with silicone spray, that will increase the insulation and likely stop it from leaking spark.