Utopia Texas

I've had my 2008 SL550 for three weeks and it has run perfectly. 38k miles of which I have put on around 500 miles. Started fine this afternoon and at a stop sign down the road coasting to a stop the engine rpm's dropped then the engine surged to 1100 rpm. At that time I applied throttle and drove on confused as to what had happened. Nothing happened for the rest of the drive with multiple stops until I pulled into the driveway and the idle speed dropped, then sped up to about 1000 rpm, then dropped and the engine stalled. Any. Ideas as to what is going on? When the rpm's drop it appears the engine tries to adjust. At anything above idle the engine purrs. No codes or anything odd appears on the dash. Thanks.....
PS- I did install the updated 2015-2016 Navigation DVD a few days ago. Does the DVD have anything else on it besides navigation?

SL65MONSTA

bad plugs maybe ? or AFM sensor on intake?

carguyshu

throttle bypass valve or map sensor possibly.

Utopia Texas

Last Friday I contacted two members of the Houston, Tx Mercedes club and they both recommended a independent mechanic shop on my side of town that they said did excellent work so I took the car in and I should hear from them tomorrow what they have diagnosed as the problem. The owner was super nice and even gave me a ride home 15 miles out of his way after the shop closed. How's that for friendly service!!! The shop was full of Mercedes, BMW and Moto Guzzi bikes. I talked to 4 of their mechanics while I was there and left very comfortable with the set up.

yovenim

My 92 RS idles fine when cold. When warm it occasionally bogs and has stalled on me twice when sitting at a light. It seems to idle the worst when I am using something electric, like the heater fan. When I turn the fan on it bogs almost immediately, then it starts to bog intermittently. If I turn the fan off it's clearly better. Also, since I got the car running a month ago after sitting for about a year, it's very slow to start cranking, then it cranks fine. I haven't load tested the battery but the battery is not old and I have filled it and have been keeping it on a desulfating charger. It's over 14 volts at idle. My dad thinks this is all related to a bad ground somewhere. Other than the main negative cable from the battery are there any other grounds that I should check that might be common points for failure? Or any other ideas as to what might cause symptoms like this?

Utopia Texas

Sorry, I can’t help out. I traded that SL in years ago. I do remember it turned out to be a purge valve at the gas tank that was stuck.

Aussiesuede

Have the mechanic check the condition of the PCV. Theyy are often overlooked and will cause intermittent rough idle and if almost completely clogged, or the diaphragm membrane no longer flutters, occasional stalling is possible.