I have a 2012 C250 Coupe with 145,000 miles that has an issue that the dealership has been unable to resolve. Initially, I took the car in for a coolant leak. They say that they replaced the leaking pipe at the back of the cylinder head under the oil filter housing. While they were in there, they suggested that I have the oil filter housing to the block gasket replaced since they would already have the manifold off. When I picked up the car, I started it and it felt like it had a misfire. I turned off the car fearing engine damage. Immediately started the car again and the misfire was gone. Next morning repeated the process. Start the car misfire, shut the car off, start the car, misfire gone. Before this repair, there was never an issue with misfire. Took the car back to the dealer. After a week, they decided that it was a coincidence and the issue had nothing to do with the initial repair. Now there is a misfire on cylinder 4. They claim that the spark plug hole was flooded. They said they changed the valve cover gaskets and spark plugs as well as swapping #4 and #1 coils. I pick up the car, still has the issue. Goes back to the dealer. It has now been there two months. No CLE light, no codes. They then tell me it is the HPFP. They replace the HPFP and that does not fix the issue. They tried to change the coil pack, did not resolve the issue. They tell me it is clogged injectors. They put injector cleaner and a gas additive. They have a tech drive it over 100 miles home and back over the course of a couple of days. Still no fix. First start misfires, immediate restart no issues. Any suggestions? After over two months at the dealer, I am out over $4,000 and I still have no idea what is wrong with my car and have no fix.

Any help or suggestions would be greatly appreciated.

 

any update on this?

 

Did you find any solution?

 

Exactly the same problem happened to me! I have a 2012 C250 Coupe with 120k miles, I'm starting to lose coolant water from behind the engine. I stopped it, changed the tube behind the engine and also the oil filter holding gasket. For that I had to remove the intake and also the high pressure fuel pump. For me the problem comes with the blessed fuel pump, I'm looking at the engine and don't forget to connect any plug. I don't think it's a spark plug or coil since the car worked perfectly before disassembling it.