Daaffeeyy

I need some help with a misfire on my C300.
History: I was on my way home from work and got off the freeway. came to a stop and the MIL light came on and the engine felt like it was misfiring.
Checked the codes and had the following: 0600, 0601, 0605, 0606 or P300, P0301, P0305, P0306

This is what I have done so far.
1. Checked fuel pressure - good
2. Checked cylinder compression - 150 +/- 5
3. Checked the MAF sensor - good

Proceeded with the following:
1. Changed the spark plugs
2. Changed the coils
3. Changed all the injectors
4. Changed all of the cam sensors
5. Changed the Crankcase sensor

I still have the same issue. any help would be appreciated.

catmandoob

I'd be looking at battery and ground connections too. Those codes tend to be PCM error codes which can influence timing etc.

Also, we assume a lot but since you had that type of work done we can safely assume all error codes were erased and came back?

Daaffeeyy

catmandoob, Yes, cleared the codes and they all came back. Thanks for the help. I'll check the ground from body to engine. Do these engines have issues with the timing chain?

gamma300C

Your thought of a stretched timing chain vs VVT sprocket problem (if an early C300) might be considered after confirming electrics up to spec.

E55Greasemonkey

Throw some more parts, time, and money at it. After that, then you can pay for a professional diagnosis.

Daaffeeyy

Well, this did not help.

Daaffeeyy

Ok, I'll continue to check the electronics first. Thanks.

gamma300C

What year C300...mileage ?

Daaffeeyy

gamma300C, It is a 2009 C300 4matic and it has 155,000 miles on it. It has been a very reliable vehicle.
Thanks,

Daaffeeyy

Car has been in the Mercedes shop for a month and they can't figure it out. They have been able to find the misfire and will run for a day then back to the misfire. Everything I replaced is what they would have done. Talked directly to the gentleman working on my car going over different sinerios and no solutions.

JettaRed

iTrader: (1)

Actually, that was probably the best advice yet (except, don't swap out any more parts).

Related to potential grounding issues are battery issues. While it may seem unlikely, the Aux battery may not be performing as it should even though the voltage reading may be within limits. That would be the only thing more I would try before taking the car in.

JettaRed

iTrader: (1)

Well, I see you did take it to a shop. A month? Did you ask them to swap out the battery? I bet they have the car on a trickle charger but don't put it back on the charger and after a day the battery drains back down. In which case, it could also be your alternator.

Has either battery ever been changed? If so, how long ago? These cars seem to be very temperamental when it comes to batteries and electronics.

Daaffeeyy

Well, Got the car back from the Mercedes shop. They told me the old intake manifold internal plastic broke apart and pieces of plastic when through the cylinders. That is why I was getting random misfire codes. 1,5,6,3. Unfortunately, cylinder 3 did not recover from the damage and the exhaust valve has a spot on it where it will not seal and will cause an instance of low compression which in turn causes the misfire code for cylinder 3, but only when cold. They said it would need a new head. So... That is what I have been doing. putting another head on the car. I'll update this when I get it done.

cvx5832

That’s nuts! Seems very plausible given the known issues with the swirl flaps though. Makes me want to replace mine preventively. Currently at 191k on my 08.

And thanks for updating the thread. Wish everyone who posted questions did that.

Odd Piggy

!!!
That “spot” on exhaust valve 3 must have been severe to require a new head. From the description “… only when cold”, I would have thought replacing the valve and dressing the seat would have sufficed.