MB S600 (Year 2001) W2201 Engine Misfire diagnosis help

[Ash Pat]

Dear Pistonheads,

I recently bought a 2001 MB S600 W2201 engine vehicle. The vehicle is misfiring in the following cylinders according to the Mercedes Star diagnostic:

Passenger side 3 cylinders and Drivers side 5 cylinders are misfiring.

I have done the following to rectify:

1. Added fuel cleaning additive to the fuel, and then put in Shell Hi Octane fuel as the previous owner was using cheap fuel.
2. Then had the car fully serviced and oil changed to Mobile 1 oil.
3. Changed the MASS airflow sensor
4. Changed all 24 Spark Plugs to Iridium OEM NGK ones.
5. Changed the Voltage convertor.

All parts were Mercedes original.

Having done all of the above, the misfiring persists and the car does not drive, it just dumps the fuel.

To Note: When I changed the Spark plugs, many of them were oil covered.

Anybody have any idea what I can do next.
Your help and advice will be much appreciated
Many Thanks.

[David Beer]

You had a full service and came back like that ?

[Ash Pat]

No, I had the full service, because I started having that issue.

[T1CHS]

Sounds like it could be the dreaded coil pack issue..... Plenty of information on the internet, there’s a chap in the US that sells new coil packs, fully tested, that are vastly cheaper than OEM from Mercedes.

[Penelope Stopit]

https://www.v12icpack.com/?_escaped_fragment_=/V12...

[TarquinMX5]

Unfortunately, it does sound as if it could be the coil packs; it's not uncommon, particularly on pre-2003 cars. Is there any history of them having been replaced previously.

Does yours have cylinder de-activation? If so, it might be worth having that disabled via STAR, as there is a view that the deactivation can put extra stresses on the coil packs, however, that's a future-proofing idea, not a fix for the current problem.