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- - 1996 Sl500 rough idle (https://mercedesforum.com/forum/mercedes-sl-class-15/1996-sl500-rough-idle-48477/)

1996 Sl500 rough idle

Hi, I have a 1996 SL500, which has a small problem. Occasionally, the RPM drops down to about 500 for a second or so as I stop at red light, the engine would give a light shake and then it runs smoothly at about RPM 550-600. At another occasion, say once a week, the engine would stall without any warring while smoothly idling as I am waiting for the green light. Usually I have to drive more than 100km before this happens. I can start the car immediately. Also, sometimes I can feel a light engine shake at a speed of about 40 to 50km/h. Any idea what may be the cause of this problem? Thanks.

the overload protection relay can do some weird stuff like that. it's a tall relay with a red top inside the module compartment, passenger side next to the hood hinge. does it do it more on rougher roads? they're a little over 50 bucks at autohausaz.com. a relative cheap try. check vacuum hoses, wires and connections first.