300CE weird idle
 

I've had my beautiful 1992 300CE for five months
now, and not had even the slightest problem with it until this strange little symptom just started appearing. Sometimes (which is to say not every time) when I start the car, for about 3 or 4 seconds it idles too high and *very* roughly and the SRS light stays on. The light then goes out and the idle returns to normal. It just started doing this for the first time a couple of days ago, but it has happened a number of times since then. Once, it seemed as if the idle was actually climbing and if I hadn't turned it off, I would swear it would have just kept going up. Any ideas on where to start with this one? Forgive my lack of DIY knowledge, but I'm a relative MB newbie.


Thanks!

Zach
1992 300CE

Sounds like your overvoltage protection relay (fuse-capped relay in the firewall behind the battery) has bit the dust. Well, either that, or the fuse has blown. If you do a search here for "overvoltage relay" or "OVP" you'll find a lot of information on the relay. stevebfl has posted some good info on it.

The good news is that if it is the OVP relay, it's not that expensive, and a straightforward replacement. The bad news is that it's a bear to pull out of the socket.

anthony

Zach-

you may wish to have a tech read any diagnostic trouble codes (DTCs) if present

-fad