Hi,

My name is Andreas I have a 2008 CLS 63. Just for reference I bought the car from the son of the original owner. The car is near mint, always garaged and 100% dealer maintained with records. The car is 100% stock, no mods. I am posting today because I need advice.

18 months ago the car would occasionally (every 15 starts or so) idle ruff when cold starting. The only way to fix it was to shut the car off and turn it back on. I told the dealer and they said no code = no problem

12 months ago: No change in the frequency but definite change in severity (much rougher idle, clear misfire on at least one cylinder). The CEL would come on but when I would restart the car it would be gone and all was fine, car was smooth again. I took the car to the dealer, they replaced coils

8 months ago: No change in the frequency slight increase in severity (rougher idle, clear misfire on at least one cylinder). The CEL would come on and stay on, even after I restarted car and the car was running smooth. The dealer determined the problem was caused by a fuel injector leaking onto the engine wiring harness. So dealer replaced both (had the car for 2 months).

6 months ago: Got the car back and was disappointed from day two when this rough start occurred again. The severity was less then it had been but still a misfire and I had to restart the car to make it go away. The dealer did a code scan and found nothing.

I continued to drive the car a few times a week (less than 2k in 6 months). The car continued to have rough idle starts with the occasional CEL that would go away with the problem once I restarted the car. This last weekend I drove the car 200 miles out of town, everything went fine until I went to start the car the next day. I started the car and it shook severely (worst I have ever experienced), had I been holding a cup of coffee I would have spilled it. The CEL light was flashing. I shut the car down within 5-10 seconds and restarted it. This time it did the same exact thing upon restart. Only on the second restart did the car go back to normal with the exception of a check engine light now on solid. This felt like a misfire on multiple cylinders.

The car went back to the dealer, They have had it 7 days , They believe that head bolts are bad and coolant is leaking into cylinders when I park overnight causing the misfire. The problem I have with this (besides the cost) is:
1: head bolts have already been replaced as a precautionary measure.
2. The car starts in a garage and I have never seen, or smelled any steam, coolant, smoke, anything at all when starting.
3. The coolant level has never been low and I check it once a year or every 10k miles.

The dealer did say that there is a chance that the head bolts are fine, at that point I would have spent $1600 and still have a broken car. I am tired of throwing money at this so if anyone has any experience with similar situation I would love to get some advice.

 

Get it away from the dealer and have your oil tested for coolant. Then you will have a starting point.

 

Replace the crank case vent valve and dump all the oil out of the intake manifold.

 

Andreas, just out of curiosity, where are you located?

Any other dealer nearby that you can go to?

Has the dealer involved Mercedes-Benz corporate yet?

Are you asking for a SHOP FOREMAN to look at the problem? Foremen are paid on salary where most automotive technicians are paid for the job by the book hours, a standard number of hours that is predetermined for the job. You need a foreman to inspect your vehicle.

 

That sounds like words of experience, and very likely a diagnosis.

 

I had a clk320 that would do this, the cure was usually restarting or clearing the code.

It turned out to be a bad coil pack on one of the cylinders. Any way you can test your coil packs?
If the headbolts are done then I'm not sure what else it could be...

 

 

Did you figure it out?

 

Hi and thanks to everyone.

I am in Santa Barbara Ca. I asked the dealer to test the oil for coolant. I was told that it would likely come back as no coolant in oil since the car was not low on coolant or smoking at all. Regarding the crank case vent valve, good idea, will try. Regarding Shop foreman, I have only spoken with my service writer. I picked up the car this morning after two weeks of no diagnosis and had not read your reply until after this. The dealer never involved MB Corporate, I did not know that was an option. Dealers only option for me was for me to spend $1600 to check head bolts.

I have an appoint for 7/9 at a local MB independent service. They want to pull the plugs and scope the cylinders. They quoted $400. They said that from this they should be able to tell if it is a mechanical issue (like the dealer thinks) or if its something else.

Is there a chance this is electrical? The dealer replaced my oil cap today when I picked up the car. He said the old one was cracked and who knows maybe thats the issue...



2008 CLS 63 AMG

 

1. MB Corporate involvement is not likely to yield much considering the age of the vehicle. But it's something you can ask for.
2. Definitely ask for a foreman to be assigned to the car, they're the ones who spend the time to look for the strange problems. They're much more motivated to fix the problem than a service man who's just trying to bill as many work hours as he can.
3. I'm still clueless to the reason behind the problem; it may be mechanical, it may be electrical.