EGR valve and oil by plug

[mathesius]

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, 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:
http://www.mathesius.com/files/oil-by-cylinder4.JPG

[Perinchery]

I have the same problem on my 96 C220.
Oil around the spark plug on cylinder 4.
Is this an inherent problem?

96, C220

[rollinrealbig]

Ok, that oil in the spark plug is causing such bad idle, get that gasket set changed, also use parts cleaner (brake cleaner/carb cleaner) to clean everything out, get new spark plugs as well and what ever you broke.

that oil is probably causing those misfires so get that cleaned and CEL turned off and that should be good.

as far as the EGR valve, if you can take it off and clean it, that would be good. if you cant, just give the car about 100miles and see if the CEL comes on and read what else it may say.

if it goes on agian, then you can try cleaning it.

although it may still go on after you clean it, and if that happens, change it. I think they are around $140 but im not so sure.

hope that helps!

[mathesius]

It turns out my EGR code was a stored code, not an active code. Since I didn't know when the codes were cleared last, I have no idea what set that or when.

Cylinder 2 misfire was the only active code per the Zimbrick dealership.

They found the center electrode on the plug in cylinder 2 had disintegrated (a bit of it was in the top of the cylinder, which they got out somehow).

I also had them do the valve cover gasket job since the price they quoted wasn't too bad.

Clean running... for a week. Then today I accelerated strongly to pass a car and the CEL came back on and the engine ran rough again. Same as before, it started with a rough idle but progressed to a loss of power at highway speed.

I took it back to Zimbrick rather than deal with this. Turns out cylinder 3 & 4 were misfiring, so they changed out the plugs in 3 & 4 -- so now all four of the new plugs I put in 6 weeks ago are replaced with new plugs they put in.

Drove smooth home. Until I accelerated strongly to test things out.

Bingo, the CEL came on, the engine got rough even faster than before. I made it home, cleared the codes by unplugging the battery, and started it up.

No CEL, ran smooth at idle. Ran smooth at 2000 RPMs. At 4000 RPMs it went bad again, causing misfires and rough running at any speed just as before.

Short story:

Something is triggering at higher RPMs that causes the whole engine to misbehave.

Possibly this is causing it to misbehave so badly that it's ruining plugs.

Any guesses?

I am running a K&N air filter, but the MAS hasn't yet sent a code and from what I can tell most bad Mass Air Flow Sensors throw codes. The dealership did warn me against the K&N though. I've had the K&N in for 12,000 miles.

I am going to do more research online and probably take it back to the dealership tomorrow.