Hello fellow Mercedes enthusiasts!
I am having a problem with my car and wanted to check if there is anyone else having this symptoms.

Mercedes CL500 4-matic BlueEfficiency, facelift, year of manufacture 16.05.2011
VIN: WDD2163941A028045
Current KM: 126900 approx
-changed spark plugs on 23.11. 2022 - OEM Mercedes - part code A 004 159 81 03 - Tightened at a torque of 23NM
-(Bosch electric motor changed at the same intervention)
-last oil change + filters 12.10.2022 - Motul 8100-Max 0w40 oil
-gearbox mount also changed 23.09.2022 OEM Mercedes - I don't know if it's relevant but it's good to know

I decided to change the spark plugs because I had noticed in the car's history that they were not changed until 1240,000 km (or at least they did not appear to be changed). The car was running perfectly.

Immediately after changing the spark plugs, I noticed a slight fluctuation/vibration at idle. The idling vibration was felt in the seat more intensely than before the spark plug change.
The car was driven like this without this vibration disappearing. I haven't noticed any alteration in terms of engine power or other larger fluctuations in revs under load or idle.

About 3 weeks after this intervention, on December 12, after it started without problems in the morning, after 10-15 minutes of driving, the engine started to run very intermittently. It stopped firing at all, there was a strong smell of gasoline around the car and in the passenger compartment. It went like this for another 300 meters until I parked it somewhere to be taken from the platform and taken to a service.
The same evening at that service, the spark plugs on the driver's side were checked, they seemed fine. A diagnosis was tried with an older Star, but no error code appeared. It stayed in the garage for one night and the next day, I pulled the plug from the solenoid on the driver's side and noticed that it had a little oil. I cleaned it and drove the car without the solenoid connected for about 10 minutes. The car was running within parameters. I put back the solenoid connection in place and drove with it like that. The vibration initially disappeared for a few hours, after which it reappeared.

On December 20th, he had the same symptoms, a very interrupted engine, smell of gasoline, lack of power. If the transmission was in P, it somehow idled, but when I put it in D or R, the idle fluctuated very strongly, almost stopping the engine.
I went like this with her to a service that did some readjustments to the mixture with a Launch diagnosis. Also during this service, the spark plugs on the passenger seat were also removed and they were all very very burnt, black. I "cleaned" them and mounted them in place. I mention that they were no longer torqued at 23NM this time.
The car started working within parameters but with the same vibration and micro interruptions at idle.

In the meantime, the coils were also changed on the advice of another mechanic without noticing any improvement/worsening of the situation. The coils are aftermarket BERU (Borg Warner).

Since then the car has been running like this, the vibration at idle is still there and I could add that on a long journey, if you accelerate more suddenly, between 3400RPM - 4000RPM you can notice small interruptions of the engine's power. I want to mention that the car had only one owner in the Netherlands who seems to have taken care of it, it also has a history at Mercedes dealerships there, but mostly oil/filter changes were made, no major intervention over time. He changed the oil in the gearbox at 115,000 km exactly before I bought it.

Thanks!

 

I wonder if multiple things could be going on. The gasoline smell in the cabin could be a cracked fuel pump ring or seal. The interruption in power could be a fuel pump or filter problem. I really don't know...maybe just expand your search parameters beyond what you just worked on?

 

I had changed the plugs for the first time in 106,000 to address a misfire. This misfire was resulting in car going into limp mode shortly after driving , if I shut the car off and restarted it would idle rough after a few minutes...alot of gas smell from tail pipe. through much frustration i discovered that the fresh plugs created a heavier draw on the coils and caused them also fail. They were the original coils. The spark plugs MUST BE the correct factory plugs. I know it sounds unimportant but the compatible spark plugs I ordered were same length, etc and they worked...sorta...but once I put the factory plugs in (NGK) and fresh coils ...all problems went away. Been 20K miles no issues. It was a real PIA.