My 1998 SLK230 has this weird behavior that whenever it is cool and humid outside, like in the morning, my check engine light will sometimes come on and the engine idles and runs really rough, like one of the cylinders is missing. If I turn my car off and let it set for a while, the car then runs fine, but the check engine light stays on, but usually mysteriously goes out a day or two later.
I've been to the dealer twice. The first time they said broken engine mounts were causing the engine to vibrate and throw off the knock sensor. I had the engine mounts replaced, which I'm glad I did anyway, but the problem still reared it's ugly head.
I went to back to the dealer and they kept it for a week, and of course were unable to reproduce the problem, and had no diagnosis.
It sounds like classic carburetor icing, but you don't have a carburetor. When cool humid air passes through a venturi it drops in temperature, and the humidity forms ice, blocking airflow. Before the days of fuel injection most engines had a thermostatically controlled flapper that mixed warm air drawn from over the exhaust manifold with the incoming cold air to prevent this. I don't know if the SLK has some form of intake air pre-heat system but if it does I'd look for a problem there.
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Classic black 1992 190E 2.6, with over 250,000 km, Silver 1998 SLK230 (sold)</font>
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RE: Here are several TBS that relate to your problem:
Thanks for the TBS! I think it might be the Mass Air Sensor. When I last looked at the air filter I noticed the gasket was damaged and the 'clean' side of the filter was not so clean, so maybe some sand/dirt may have damaged the sensor. any idea how much a new one costs + labor to install?
RE: Here are several TBS that relate to your problem:
Well, a new one is only $113.00 (part # 111 090 00 01 - for 1998 model). I think it is a DIY project. Now days with the digital camera available, just take several pictures of the area, before removing it, to make should you put it back right.
RE: All you guys might think that the MAF goes bad because of the aftermarket air filter but
I prefer not to spend the money on a K&N filter that I have to do maintenance on, for only a questionable "1" horse increase and another questionable MAF damage.
Linear Mode
