Hi guys,

New to this forum. My name is Emiel, from The Netherlands and drive a 2014 W205 (t modell c-class so officially a S205) C200, petrol, a/t, 70.000km .
Issue we have: a misfire in one of the cylinders.

What has happened so far:
Indie replaced the plugs and coils approx 3000km ago (free of charge under 6mnth warranty)
Cleared the P-codes (one was a generic 'misfire' code).
The car got an official software update about a week ago. Don't know the version or other details.
Replaced air-filter because it was clogged (never got changed)

Current situation
Still having misfires.
Yesterday we removed the coils and plugs to check the plugs. 1, 2 and 4 are clean ('Sahara'/beige color which indicates a healthy situation). 3 is like charcoal, already (after 3000km). Forgot to take pictures.
No P-codes at the moment.

Data:
Bought myself a simple OBD2 scanner to check the engine data (idle and while driving).
A few observations;

Scenario 1;
Easy 0-80km/h pull up: switch on cruise control at 80km/h (or keep a steady foot). We live in The Netherlands so flat roads with very smooth asphalt :-)
Engine load remains at approx 20% for a while but suddenly sparks to 40/50% and doesn't return to 'normal'. Sometimes after 20 seconds, sometimes after 1 minute or everything in between.
Also at the exact moment: o2s11 goes from a steady -0,008/0,008ma to 0,7/0,9/1,1/1,4ma, in other words it's going all over the place. Lambda11 is also having a rough time keeping 1 > 1,4/1,7/1,8
This situation results in (or perhaps more precisely is the result of) misfires. Engine stutters and is very present in the car (you can feel the engine stutter, it is very noticeable).
These values keep going all over the place until the moment I take control by e.g. increase speed (increase cruise control 10km/h) OR switch off cruise control OR accelerate manually.
After increasing speed (and with that revs) and stabilizing the situation repeats itself. Engine load 20% goes to 40/50%, o2s11 from steady to all over the place, lambda is all over the place.

Scenario 2:
0-50km/h > just the same result as scenario 1. Stuttering even more noticeable.

Scenario 3:
120/130km/h > revs are above 2000rpm > values seem to stay normal (or at least normal for longer). It is difficult to notice the engine stutter because of the speed and regular vibrations in the car.

Other info:
Misfires seem to happen when the engine is hot. In other words: cold-start > drive off > don't experience issues > temperature increases to operating temp > issues start.
Perhaps because sensors are not activated or not in operating temperature window? I don't know.
Cruise control (incl. distance control) has nothing to do with the issue. We experience the same situation when driving manually (with 'a steady foot').

My thoughts:
- Bad Mass Airflow Sensor? > no code
- Malfunctioning injector (but less likely because it is not experienced all the time)
- Bad o2s11 sensor?
- Bad intake manifold?

Any thoughts?

Didn't focus on other values but please tell me if more info or additional data is necessary.

Thanks guys!

 

Sorry about your issue. I recommend you keep your mechanic away from it since he was not able to fix it. This is a serious problem and must be fixed ASAP. There is something wrong happening when the car gets hot. You are wasting your time and money by guessing. Since your mechanic was not able to fix. I recommend you visit your local dealer and get it fix once for all.

 

Thanks for your reply.
Perhaps I shouldn't use the term 'indie'. It was diagnosed by both the official MB dealer and an MB specialist. The dealer referred me to the MB specialist since they were unable to locate the issue themselves. The update was performed by the official MB dealer.
The specialist is considered a true specialist but unsuccessful so far.
That is why I now turn to the 'wisdom of the crowd'.

 

What? If MB dealer is unable to fix the car، who is going to fix it? Why is this dealer referring you to others to fix a MB car. This is a strange story. I can tell you about my dealer they wont quit until they fix the car. Did you try another dealer. How about MB of Nederland head office do they know that your dealer was not able to fix your car? That is really embarrassing.

 

I bought the car from a generic dealer. Don't get me wrong. The MB specialist I'm referring to is not some sort of local town hero with a lift. The MB dealer frequently works together with this 'guy' when the issue is difficult to diagnose. The MB dealer will do the repairs.
So believe it or not. This is the situation 😀

 

MB dealer is refering a MB owner to some guy to help fix a MB car. This should be the headline of the Best Or Nothing Newspaper. Keep us posted.