TANSTAAFL

Betty Rubble is an 02 ex with 240k. Had her parked for 18 months after two cylinders were misfiring. Main problem was oil seals on spark plug tubes. I had one coil pack go out. Replaced all four. Two of the new packs went out within a month. She was running really rough when parked.

Recently replaced valve cover gasket, spark plug tube seals, rear cam seal. Oil leak appears to be resolved. Plugs (NGK) and coil packs (Denso) were replaced as well.

Engine light came on within first thirty miles. Went to the parts store to pull codes last night. Had misfire/ bad plug in cylinder 4 and a catalytic converter code, reader did not give numbers, only description.

Pulled the plug from cylinder 4 and it looked like this after 100 miles.

Engine runs rough between 1500 and 2000 rpm, otherwise it seems fine. She says ba bump, ba bump, ba bump unless accelerator is pressed through this rpm band.

Compression is good in all cylinders. As only one cylinder seems to be affecting I don't think it is a timing issue. I will clean the air filter tonight (k&n).

What is the most likely culprit? Dirty/stuck/bad injector? The CC? Dirty intake?