98 C230 Check Engine Light

I have a 98 C230 with about 135K miles. In the last 3 weeks, my check engine light has been coming on and going off. I called the Mercedes roadside service, and they told me that the check engine light is related to my car's fuel system. Unless the car stopped running or had symptoms of a possible breakdown, I was advised by Mercedes to wait a few days and see if the light goes off. If it does not, then I should schedule a diagnostic with my mechanic. Well, the light went out after a couple of days. Later it the week when my fuel was low, the check engine light came on again. I filled up the tank, and, of course, after a few days, the light went off again. Over the weekend, I took the car for an emissions test. (I live in a county in the state of GA that requires emissions testing.) The gas cap test failed. However, everything else passed. I was advised by the emissions testing facility to replace my gas cap. Once replaced, I should return and re-test. I took it to a Mercedes shop that was open on a Saturday, but this was not my regular mechanic. On my way to get the gas cap replaced, of course, my check engine light came on again. The Mercedes shop advised me that the cap itself does not need to be replaced. However, I needed to replace the rubber ring inside the cap. (This ring served as a seal.) After the rubber ring was replaced, I immediately took my car back to the emissions testing facility for a re-test on the gas cap. Yes, the re-test was a success. However, my check engine light is still on. I am waiting for the light to go off again.

Has anyone ever had this problem? Should I get a diagnostics test done which will cost me about $100? (I don't feel compelled to rush to my mechanic and get the check engine light diagnosed because the car is running fine.) Or, do you think that the rubber seal may have been the cause? Any feedback will be greatly appreciated.

I say if it passed the emissions test and everything seems to be running ok just wait a couple days to see if the light goes out. If it doesn't go out in a couple driving cycles then take it in and have them run a diagnostic test. Hopefully all they have to do is erase fault codes but with a Mercedes it could be a lot of things. Best of luck to you!

I'm really suprised they just didn't replace the whole cap as they are only around 7.00 and that removes that possibility off the map completely. It's possible the EVAP system may be at fault but as Blindside said it could be anything.

My wife forgot to tighten the gas cap on her MB and the check engine light came on. I would wait, I think they told me it takes 20-30 ignition on/off's for the light to reset.
Good luck.

I Know what it is Mine was Doing that and it is the airflow Mass Sensor it cost me $430 i lost horse power because of it i have a 1999 c230 kompressor just get it check after the light stays on after a few days