John Marshall

2010 C63, 80k. I've had this car for a year, and what started as a rough idle/running/hesitation that was rare and mild has now progessed into the "don't you dare try driving me" scenario. Car has straight thru pipes, cat deleted. No CEL. Black smoke upon hard acceleration now.

codes are
P0300 multiple random misfire
P0302 misfire cyl 2
P0306 misfire cyl 6
P0307 misfire cyl 7
P0308 misfire cyl 8
P0036 HO2S heater control circuit (bank 1, sensor 2)
P0056 HO2S heater control circuit (bank 2, sensor 2)
P2237 O2 sensor positive current control circuit/open bank 1 sensor 1

It feels like a bad MAF, but disconnecting the MAFs doesn't improve much of anything (maybe a tiny amount), and I've replaced the plugs and sprayed the MAFs down with CRC cleaner (though where to clean it exactly was sort of a mystery, as I couldn't find a wire sensor).

Anyway, if someone has any ideas, I'd appreciate them. Dealer has my 2012 C300 right now diagnosing a major driveline failure (parts blew out of the car at highway speeds yesterday).

thanks

chrisridebike8

Sounds like bad upstream O2 sensors. get the bosch ones so you don't pay the MB tax as much. Also, since you are catless, I assume you have a tune. If not, that's no bueno.

AMGonFire

John Marshall

Thanks!!! Will do!

Schulminator

Denso units seem to last longer than Bosch....

SROC276

John Marshall

O2 sensors replaced, car runs perfectly again. Thanks for the help everyone!!

AMGonFire

tphss

Nice diagnosis, good to hear it's sorted!