2003 MCS with 115k miles

A month ago my SES light came on and produced a P0302 code. I promptly changed the coil, plugs and wires and reset the SES light. I've since put on about 500-600 miles without any problems. Last night, the DSC and SES lights come on and engine running rough with lots of hesitation. Pulled over, turned the motor off. Restarted after about 5 mins and it ran like normal. The DSC light went away but the SES light remained. I read the codes and now have a P0304.

I read some old posts about similar symptoms but the OPs didn't state the outcomes.

Any idea how I should proceed? I'm fairly handy but not a mechanic by any means.

Thanks!

 

What plugs did you put in? What are they gapped to? Did you goober everything with dielectric grease? If so, wipe it off.

Compression test? Timing? Fuel pressure?

 

Since that is the Cylinder 4 misfire code I would definitely check the plugs, wires and compression. Vacuum leak a possibility. I assume you are using premium gas. Worse case scenario would be a burnt exhaust valve but I wouldn't be concerned about that until the other variables are eliminated.

Drive Hard. Drive Safe. Keep Grinning.

 

Thanks for the replies so far.

I put in NGK-BKR6EGP from my local parts store and gapped them to 0.032. I didn't use any dielectric grease. Also, yes, premium gas 91 octane.

I'm going to pick up a loaner compression tester today.

Also, how do I check for a vacuum leak?

I'll report back the compression numbers once I have them.

Thanks.