Hi, I have a 1998 C230 and on my way to work the CEL came on. I didn't notice any problem at highway speed but when I came to a stoplight a rough idle was obvious. The car has 91k miles on it. I bought it 6 months ago with 79k miles.

I put in a bottle of heet, topped up the tank with fuel, and drove it home later in the day. On the trip home (41 highway miles) there was an obvious loss of power so the situation was getting worse. I stopped by Autozone and got the codes read. They said cylinders 1 & 2 were misfiring and the EGR valve was also indicated. The exact codes are P0301, P0302, P0300 and P0400.

They suggested I clean the EGR valve with some carb cleaner & try and clean the tube that goes to the intake manifold.

I found the EGR valve way at the back of the engine, very difficult to get at. Have other 230 or 230K owners accessed this? Any tips?

It seems 280 owners have problems with the tube from the intake manifold and it can be tricky to clean. I'm not sure if 4 cylinder owners tend to have the same issues.

While I have things apart, I took a look at the plugs and wires which I replaced about a month ago. I used OEM plugs and Magnecor wires and everything went great except I had a heck of a time getting the spark plug connector out of the plug hole on #4. I ended up replacing the spark plug connectors because I wanted new parts on hand in case I had to get very aggressive with it.

So when I checked, I have oil in the spark plug compartment around cylinder 4. My best guess is that in my efforts at getting the plug connector out I damaged the spark plug seal between the metal sleeve and the valve cover. So I guess I am going to need to replace the seal. Since the spark plug seals come in a kit with the valve cover gasket, this would be a good time to pull the valve cover, check it, clean it, and replace the gasket on it too.

Ok, so my question is ... do you think these two problems are related?

Thanks in advance for any help!

Here's a picture of the oil: