1997 C280 Rough running
 

I need help, at the end of my rope here. I have a 97 C280 with 175K on it. The problem is it will run great one minute and the next cough and spit terribly. When it is in it's bad mood, it idles fine(700-750 RPM)but when you try to give it the juice it wont go above 1000rpm without spitting and sputtering while black smoke belches out the tail pipe. I ran the codes, the only thing it showed was misfire on different cylinders and it got a MAF fault one time. I replaced the fuel filter and the MAF but no luck.

Not sure where to go next, any help is greatly appreciated.

Do a search. I think the spark plug connectors are a common problem on those.

As mpolli said the spark plug connectors are a problem area. The short ones underneath the coils. Could be a bad coil too, but this is an easy problem to track down. Look at your codes and it should tell you which cylinder is misfiring.
Once you determine which one it is then switch the connector with a different coil and see if the misfire follows it. If it does you found it. If not try switching the coils. Good luck.

C280 rough runiing
 

Thanks guys, I'll give it a try over the next couple of days. This is my first time with a Mercedes, a bit harder to problem solve than my Chevy Truck.

Havent washed the engine lately have ya?
Gilly

280 rough running
 

No...probalby about 8 months ago.

I do have another question though....If it could possibly be the spark plug connectors would it explain that sometimes it runs great(only about 5% of the time and for a short period) and most of the time it won't rev above 1000RPM without cutting out?

Thanks for all of the help.

I have a c230 that had bad connectors and yes sometimes it ran fine. If it doesn't cost you anything to switch the connectors around why wouldn't you just do it and see what happens?

C280 still running bad
 

Looked into the spark plug connector solution today, replaced all three and the spark plug wires as well. It looked like one of the plug wires was arching and didn't feel like it was pushed all of the way down on the plug.
Started it ...sounded fine, buttoned it back up and ran it down the road. 10 minutes later it was doing the same thing.

It smells like it is overloading with gas sometimes and starving another time. Could there be somehting wrong with the fuel delivery system?

The plugs were a little black but what did look weird was the bottom of the plug where the spark occurs, the one part of the contact looked very fragile. I pulled another and it looked the same. I thought it was normal so I proceeded without changing. The more I thought about it, it just doesn't seem right. Most spark plugs I have looked at are a bit more robust in that area.

Any thoughts/suggestions please.

Did you replace the connectors under the coils. Thats the area that causes the problem.

haha that brings back some memories...

George,

Replaced the connectors and the plug wires. Took it out for the test run, ran great for 10 minutes and then went bad again. Limped towards home at about 2MPH, got lucky on a downhill run and got it up to 15MPH and then going up the next hill it miraculously recovered and I headed home. Once I turned onto my street, it went bad again but I was able to get it to the driveway. This morning it fired right up and it ran great but I didn't take any chances.

I finally resolved myself to the fact that it is a bi-polar car and I needed professional help....the tow truck took it away at 11am this morning.

When I know the diagnosis and cure, I will update the thread with the information for everyones amusement and Information.

Thanks for all the offered solutions and help.

Did you try George's idea? Could be a coil. They can go bad and be heat sensitive.

Still a problem
 

The car is still in the shop....

they found the Oxygen sensor had some strange readings and they replaced it. From what I gather the sensor is supposed to read from a range of .1-1.0 normally(the service shop's explanation, I may have not heard him correctly). Anyway, when it is running rough, they are getting a negative reading? It is causing the car to lean out thus causing the problem.

they checked the fuel line pressure, everything is ok both when it is running normal and when it is acting up.

Is their anything else that you all can think of that might help me give them a clue...

I went through months of hell with the same problem. I changed everything without success. And I mean everything!

The final fix was one new coil. There is no test on the coil I can do to prove it was bad...it is just that the car now runs a sweet as a new one.

You have three coils. I suspect that one is bad. You have to try each of the three positions or buy three new coils. They cost $35-65 each on eBay or online Merc stores.

http://www.***************/search/product.aspx?sid=jw52q2nbux2s0tvwq024kd55&makeid=800016@Mercedes&modelid=1195499@C280&year=1997&cid= 25@Ignition%20Parts&gid=7060@Ignition%20Coil

Oz,

Thanks...I would have thought they would have checked that but I can't be sure. I am going to visit them today and will ask.

Again thanks. It was recomended previously but I gave up before I tried that.

John