P0304

[jaekl]

Back ground, I have a 96 SL1 and is just under 205,000 miles. It's been burning oil the last 60,000 miles or so at about 500 to 700 miles per quart. It's been missing some beats and the SES light comes on from time to time and the code is P0304, number four misfire. About a week ago I changed the plugs and number four had a lot of deposits. So I figured the oil burning is catching up to it. However, with the new plugs, it soon started to miss again and it is still coming up with P0304. I pulled number four plug and it is all black. Number three looked normal.

Question. Since oil burning should affect all cylinders, could there be another cause? Being number four, I'm thinking of an EGR issue and will do a cleaning shortly. Now some theory. I would think the computer can only tell if the current to the plug is faulty, (the way the voltage drops) which makes me think there is possibility that it could be an ignition issue and the deposits are a result of no fire. Or are the deposits from a mechanical issue which foul the plug?

Before I decide to pull the pistons and drill the holes in the groove, I want to exhaust (pardon the pun) all alternatives.

Thanks,