I am having a different but similiar issue that has the dealership stumped. The SDS test came back with codes 0629, 0633, 0641 stating misfires on cyl 1&4. They believe exhaust back pressure is the issue however this tune / header setup has worked fine for 2 years and then suddenly won't run ???

 

North 44 posted in another thread that his intake manifold bolts were loose and needed tightening (they were causing a vacuum leak). Maybe you issue, he said it was common...

 

Dealer will always blame something else, if i had your problems i would take the headers off and flash the ecu to stock and bring it to another dealer and see what they say. GL

 

So misfire codes are sometimes really fun. They are hardly ever current. I do not agree with the headers causing low back pressure. Misfire codes are set from a deviation in the crankshaft speed between cylinders firing events. The ecu monitors engine rpm on a 60-2 trigger on the flywheel. What it can see is the engine speed up and slow down in between firing events. This should be the same for all cylinders. If one cylinder does not speed up the crank as much as the others then that is a misfire. Now what causes that event. It happened maybe 2-7 times while you were driving but not at all at for the technician. We get stored data of what was happening when it occurred. But this is mostly time, temp, load, rpm. You do have to understand the dealership and technician are in a tight position with this sort of stuff with warranty. If we replace parts that are not bad without approval from Mercedes as part of their diagnostic path then we do not get paid. I would say that with a full bank of misfires that it might be and o2 sensor. I would have to see more data. If there is a leak in the exhaust that the o2 sensor is picking up then this could happen. Misfires are a very hard to diagnose if they are not current. I have seen bad coils on 6.3 motors but no injectors. I might look at the intake for leaks but I have not seen the bolt issue mentioned. Vacuum leaks are actually pretty easy to detect by spraying the engine with brake clean and looking for a change in the running characteristics or watching the o2 sensor readings. This is dangerous so do not try this at home. The crank case ventilation valve leaks as I stated earlier. Fuel is always something to check. Did you just fill up? Maybe a different station although that does not mean anything for sure.

 

Don't just retighten these. They are "Tension Bolts" that once they come loose should be replaced....

 

The car is now misfiring 100% of the time and the dealer has current codes. It has been at the dealership for a week now. They pulled my ECU so that I could have the tune replaced with another which I had planned to do anyway. Itwill be back on Tuesday. They were afraid to force stock software back on the ecu because they have bricked several ECU's in the past. I have had occasional cels with no symptoms since the tune was installed. It is usually P0455 large evaporative emissions leak or something like that. I clear the code or sometimes it just goes away on its own.

 

Well with good reason the cars are being ran with engine management software that was not designed to the spec of the vehicle. Did you not just read that the dealer replaced the battery and fuel pump in the other guys car due to the tune being bad?

 

Well the first thing I do if I have a current misfire check for vacuum leaks then swap coils. It is fast and eliminates ignition. If that does not work then I pull the plugs and check them to make sure there are no problems. Fouling etc. Then I pull the fuel rail to swap an injector or two depending. I assume that they have checked fuel pressure and these things and have not found anything.
If I have good compression, spark and fuel pressure then if you had a full tank I would either drain the tank or run the car on a top end fuel cleaner attachment with fresh fuel in it to eliminate bad gas. If you have current multiple misfires of the whole bank and these items check out ok. Being that you do not have a catalyst to get plugged then I would reset adaptations and if this did not work then I would lean to the ecu. I would imagine that this is where the dealership is now.
There are good and bad technicians at almost all dealerships but I have never seen one that would let a car go this long without getting a shop foreman involved. Good stores were the guys talk to each other normally we start asking each other for help pretty quickly if something is not pretty obvious in an hour or two.

 

I'm new to this and hope this is the proper way to get information into the forum, whether helpful on this thread or not.

Separate events of interest on our C63 AMG : The first at 7.8K Code 0810 thrown and traced to a leaking air injection shut-off valve on the driver side head. The car was at the dealer one week until the part was taken from a new C63 to fix.

The second CEL was a 11.2 K miles . This time the problem was in "the 810 airflow of secondary air system" of the right cylinder head. The secondary air passages in the exhast port were coated with excesive carbon which was cleaned with...pipe cleaners. (no, not roto rooter, the smoking kind). No parts were replaced. It is possible the car had not been driven hard enough ( always up to temperature , though). No further problems. We are using more throttle now. It is not a track or drag car, only local, freeway and mountains. No drivability issues were evident in either CEL incident. The 2nd CEL was NOT self erasing, once set.

This may be a separate thread (editor will break out?). The car has the AMG LSD and required special lubricant. I purchased Castrol SAF XJ 75W-140. It is made in Germany, packaged in Japan, and sold in quart cans as Castrol. I finally located it online at Perfomance NIssan , stocked for the GT-R-R35, under PN KLD4U-75401 P. My friendly local NIssan dealer wanted $75/qt. I purchased on line for $45 plus shiipping. The car took 1 3/4 qts., so I over- bought due to false call out in the owners manual of 2 plus quarts.

 

Interesting story... I didn't know we could get a CEL by driving the car gently? I guess I will have to red line it a bit more!?!?

 

I sent you a pm, Yuille36. Which dealership has the computer with the old software? I have a recurring P0455 evap leak that my dealership, ASC, cannot figure out what is causing it.

 

^^ yes indeed carbon build up from stationary vehicles or vehicles not driven appropriately to allow the carbon to not settle or collect on any type of scaffolding is a huge problem. Car needs to have flow of emissions and by-products as a result of being driven relatively aggressively from time to time at a very minimum...

 

No further CEL after clearing the last one. Wife is driving harder. Motoman