Hello everyone,
I have a 07 clk550 with about 21k miles now.
Today I got my cam plugs changes along with oil change. I saw the mechanic take off both the top covers in the engine bay and under covers underneath the engine to do the work. After the work was completed the car idles slightly rough but drives fine. This happened once but when I put the car in reverse after it was in drive the car died on me. It started up fine right after. This is all happening after the above mentioned work done as before the vehicle idled perfectly fine. Please note its a slightly rough idle, just enough for me to notice it. Any ideas what went wrong during the work done?

Thanks

 

The only two possibilites here are 1) he didn't seat the air cover fully over the MAF sensor at the rear or 2) he damaged something during the work.

 

I'll bet $20 it's the engine cover - either he didn't snap it back on tightly over the MAF intake, or he forgot to attach the hose from the secondary air pump.

 

For a w209, it is not easy to install the engine cover incorrectly.
I change my air filters many times and it's very easy to tell if the engine cover does not sit properly.

 

I hope your right because this started after the work was performed. Im taking it back on saturday and will post an update then to let you guys know.

 

Mis3, it is easy to not get the cover seated on the M273 engine. It's not quite as bad as the M112/M113 cover, but possible still. Also, there is the air pump hose that has to be reconnected, and people often forget that.

 

+1^ ~ common problem with M272/273 engines!

 

By air pump hose, do you mean the two air hoses in the front?

 

No, the M272/M273 air filter housing has an additional port for the input to the secondary air injection pump. See #3 and #4 in this diagram:

http://benzbits.com/w209/EngineCover.pdf

 

Ok guys I took my car in yesterday to the same mechanic and you guys were right, the engine cover was installed incorrectly. After installing it properly my vehicle is now back to normal operations. Also he confessed that he ran the car for little bit with the engine cover off after he installed the cam plugs to insure no leaks and he said that might have also caused some problems. Do you think running the car without the engine cover was a bad idea on his part? If yes what type of damages might have occurred?

 

No damage. Just would have left the MAF hunting around trying to get mixture correct.

Pleased it's sorted.

 

There would be no damage - just as Glyn said, the ECU was "hunting" to get the proper mixture. Now, the question is, who's going to send me my $20???