RCTRYAN

I have been battling this situation since Ive owned this car 2009 c63. (CPO purchase 4/12.) Bank 1 seems to run a lot richer than bank 2. Ive pulled out the plugs several times and the plugs in bank 1 are always more burnt to a point where it is almost fouled out. Which leads to a hesitation under partial throttle between 70mph-90mph. My exhaust tips on the passenger side are also significantly darker due to the soot within 1000 miles. I have brought the car to the dealer several times as well as different dealerships and they always told me that everything checks out okay. I was wondering if anyone has any suggestions or experience with the situation I am experiencing. Thanks in advance.

BerBer63

change 02 plugs on richer side

Mort

Might also get some MAF cleaner and give them a good spray since one may be slightly dirty affecting it's performance but not enough to throw a code.

Small air leaks may also be a possibility on the leaner running side. Maybe not a big possibility because I think the system is very sensitive to lean conditions and it will throw a code.

RCTRYAN

Thanks for the advice guys, I have swapped the 02 sensors left to right and evaluated it after 1000 miles and no change. Bank 1 still has more soot on the exhaust tips as well as fouled plugs.
I will try swapping mafs from left to right. I will keep you guys updated.
Thanks again.

Merc63

Is it tuned or stock???

How are your air filters?

RCTRYAN

Air filters are new. I currently have kn with cd. Car is stock. Not tuned.

cyberorth

Doesnt the intake combine left and right inlets anyway?