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,

[jaekl]

Any comments, suggestions, encouragement?

[madpogue]

Oil consumption doesn't necessarily affect all cylinders. Depends on the condition of each cylinder's oil wiping ring, and each cylinder's valve guide seals (the two big causes). But before thinking it's a serious oil problem, do a compression test.

[jaekl]

I finally had a chance to look at the car. I found the terminals on the coils highly corroded and loose. Swapped in a set from another car and drove it for over an half hour and swapped plugs from no.3 and no.4. Definitely running better and no SES light. It runs fine except around 1500 rpm in high gear (auto), not so much as a miss as jusst rough. Pulled the plug when I got back. The blackness on what was no 4 had cleaned up, but the new no.4 was showing some black coating. I have to think about that but I think it still tells me something mechanical is fouling the plug. I'll have to get a compression tester.

I see the new plugs are Champion double platinum. what exactly happens when the platinums are used?
Thanks

[fdryer]

Your Saturn S-series ignition is described as a "waste spark system" that sends spark to 1&4 simultaneously (2&3 with the other ignition coil). If spark goes to one plug in one direction the other plug gets spark in the opposite direction; spark jumping from center tip to base while the other plug has spark going from base to tip. This begins eroding platinum plugs, effectively eating away the electrodes and any advantage plats have over plain copper plugs. Since plats are not recommended for the S-series and almost everyone thinks plats are the rage, S-series owners learn the hard way about misfiring platinums unless reading about them here on Saturnfans.

Platinums are designated as factory plugs ONLY when specified in the owner's manual otherwise its just plain second guessing the car manufacturer by substituting known good plugs with plugs designed to run in engines for 100k miles. Only those cars that came with plugs with 100k mile replacement intervals use platinums. They just don't work in your model, period. If you use them you will suffer later down the road as some have found.

Use dielectric grease on the terminals and boots as it serves two purposes; easy lube to prevent baking the boots onto parts and as a corrosion preventative.

And you're driving an oil burner that's basically a mechanical issue; as mentioned - valve seals/guides or piston rings stuck from carbon deposits removed only by a rebuild.