MERCADIAN

Hi all,

Ive recently noticed that my fuel consumption was deteriorating along with some slight white smoke from the exhaust so i decided to purchase a Foxwell NT301 code reader and sure enough my LTFT on both banks is showing + 20 % so I booked it in with my local Mercedes dealership for the full diagnostic treatment and they tell me that there is no CEL showing and they can’t find any faults with car whatsoever and they were even kind enough to give me a copy of the xentry diagnostic paperwork.

After looking through the xentry document I can see a substantial difference in the O2 sensor readings which must be the cause of my initial complaints to the mercedes dealership ?

WRC-LVR

Take it back and tell them NO its not normal according to the data they looked at . The two sensors are not matching up. Could be the O2 sensors or cat, but it will also need better diagnosis

White smoke is usually water condensation or coolant so could be a head gasket or other leak getting coolant into the cylinders. If the white smoke disappears after a few minutes, its usually condensation from the cats warimng up. If you stand behind the car with the smoke coming out, does it smell like coolant? if no smell, then condensation is most likely. If smoke is continuous, may mean coolant is being burned.

Check the coolant level, correct if necessary and check again after 2 weeks. If it goes down, you have coolant being lost.

cruiser02

Wow! This is why I don’t trust dealerships at all. I would find a good independent Mercedes only mechanic to look at it.

This is even more funny because it clearly shows incorrect performance. And even if it was normal, why is the other not behaving the same?

FYI my car was misfiring, driving roughly, and slight white smoke due to a bad O2 sensor. The oil went through the camshaft sensors, in the engine harness, and all the way to the O2 sensor. The harness was throughly cleaned and sensors replaced and it’s been running perfectly since.

Hope you get this sorted soon, let us know.

BOTUS

As CAT sensors age they create interesting interactions with fuel trims - the car runs OK but fuel usage goes mad.... resetting the adaptions works for 200 miles then the insanity returns - over and over

I presume its some interesting "software" trying to sell a new car - when really all it needs is a new CAT sensor that provides a volt reading just inside the envelope for normal fueling

BMW motorbikes do this exact same thing - got to love Bosch (I wonder which country this stuff is designed in - oh yes - that one again !!!)

and likely the reasoning behind this need when tuning BMW to run correctly https://www.beemerboneyard.com/bmwafo2sema.html