Velorate

Hi everyone,
there doesn’t seem to be too many ppl in the B-Class forums but here we go:
I have a 2011 B200 Turbo 6spd manual with a rough idle. Everything seems as it should when driving normally. Plenty of power etc.
only when idling, you feel the engine kicking a little. It’s random, not rhythmic.
i just had the spark plugs changed at the dealer but no change. It threw a CEL for a miss fire on cylinder 4 once. I cleared it, still idles rough but CEL hasn’t come back.
if anyone has any ideas of how to solve this, I would be very grateful.
All the best to everyone out there reading this,
Rob

Hey Hoser

Hi, are you able to use a code reader, see if any codes displaying?

Velorate

Hello,
yes, I used my own little reader and it showed the code: P0304 and description was «Cylindre 4 misfire detected »
thanks

Hey Hoser

Right, sorry, didn’t pick up on that, can’t help, except maybe throttle body clean, or air cleaner, etc?

sargt

Did you ever figure out what was the issue as I am having same problem.

Velorate

there are a few vacuum valves on top of the engine. My mechanic replaced one (not sure which one) and it helped but didn’t correct it completely. I also recently replaced the timing chain tensioner.
i have to add…the most important thing…make sure you’re using the correct top grade fuel. When I got the misfire code, I was running on 91 octane. On the inside of the fuel door, it recommends 98 RON which convers to 93 AKI for Canada. So I only use 93 or 94 octane now and haven’t had any running issues or codes since. Also make sure you’ve followed the spark plug change interval. Lastly…and the most costly would be coils.
needless to say, I don’t know what the fix is…but do everything you can to eliminate the obvious problem areas.
let us know what works for you!!
good luck