Thanks,

SirJag

 

Hi SirJag
Are you sure it is not a bad cam position sensor? I just read a post on the Mercedes Benz website about a member there who was asking about this coil and cel issue. It seems that on a cold start, the engine has a rough idle and CEL light is on.
Another member sugguested that it is a bad cam position sensor.


Did you replace it?

Jim Lombardi

 

Of course a bad coil CAN cause a CEL. Thats what a CEL is for. Get the code read to find the causes though. Now,, that said, sometimes an intermittent bad coil will NOT light the CEL.

 

Been there done that with the intermittent coil problem. When it finally threw a CEL, I was able to figure out which one the culprit was and replace it.

 

A failing coil can cause problems w/o throwing any codes. Coils can cause intermittent problems that are difficult to diagnose depending on the failure point.

Most of the time when you suddenly get a CEL and a rough idle - one of the coils has gone - and you often go to the next level with a blinking CEL.


As noted since you have a CEL you need to pull the codes on the light and work from that point.


Mercedes does have an issue with both the cam and crank sensors - they fail on a regular basis ...........so most likely that is why they were suggested.


The Jag coils are no more prone to fail then any other car. Certainly nothing like the coils in Porsche/ Audi/ VW vehicles -- they are unbelievably problematic.

 

Hi Jim,

No... I haven't replaced the cam position sensor yet. I asked because my mechanic seems pretty certain the rough idle is due to the ignition coil.

One code thrown was CAM POSITION SENSOR error, as you know. I assumed that was not the cause of the idle issue, but simply another issue I need to address.

Is there any way to CHECK the cam position sensor short of replacing it?

Thanks,

SirJag

 

A true test would require a test jig far more costly than a repacement.