bhpplease

Hey guys,

I hope you don't mind me posting... another thread!? I wasn't sure whether I should attach to the "running lean" thread - I decided to start a new one, for a new problem.

Anyway, I cleared the codes last week and engine light has come back on. This time it was caused by: "P0175" (OBDII code). Also, when reading the codes for the "Engine Control Module (MED97) for combustion engine", I receive the following "current" codes:

* 0097 - B16 (Right temperature sensor upstream of NOx storage catalytic converter)
* 0750 - The mixture (cylinder bank 2) is too rich.

(There are also historic codes for 0101 and 0746 - left sensor and bank 1 too rich)

I am writing this new post because I am wondering if I need to replace the temperature sensor related to 0097. A site has also mentioned that this code could be cause by a vacuum leak, so perhaps the first course of action is that vacuum leak needs fixing?

Thanks guys - I really appreciate the help.

Conor

P.S. I live in London, and rarely drive the car hard or on long arduous runs. 85% of driving is stop/start in town. Does this have any significance here (or anywhere).

bhpplease

Hello.

Just a quick update on this one.

I have recently fixed the running lean issue by fixing a vacuum leak. I cleared codes and had some error free driving for a while but I have recently received the rich errors again.

Also, my car has consumed about 2 litres of oil in the last 600 miles...which is completely insane. I'm not sure if it's a leak or if the oil is being burned. There is never any oil on my driveway so I am dubious about a leak.

If it's not leaking - what are the kinds of things that could cause my car to burn that much oil? I read recently that if the engine is running rich it could be fuel washing the oil off the cylinder walls etc?

I plan on brining this to a mechanic in the new year when they re-open but would also like a bit of a hint as to what might cause this?

* Bad spark plugs?
* Head gasket?
* Cylinder wear?

Sunnyslope48

https://www.autocodes.com/p0175_mercedes-benz.html

P0175 Mercedes-benz Description This fault code is stored in the Engine Control Module (ECM) when the ECM is no longer capable of controlling the air fuel ratio. For correct operation of the catalytic converter the ECM is required to keep the air fuel ratio (AFR) at approximately lambda 1, this equates to an AFR of 14.7:1 by mass. This is achieved by trimming the fuel mixture to the required amount to cater for slight anomalies during normal operating conditions. However when a fault causes the fuel trim to exceed a predetermined level the malfunction indication light is illuminated and a limited operating strategy is employed. The pre-catalyst exhaust gas oxygen sensor is the primary component used for calculating the fuel trim once the system enters closed loop control. The fuel trim data can be displayed as a percentage, either positive or negative. Under this condition the fuel trim data will display a negative value. The ECM will decrease the injection duration to counteract the excessively rich mixture. This fault can be stored due to a faulty coolant temperature sensor, excessively high fuel pressure or a faulty fuel injector. The fuel trim is monitored under various loads and conditions. If a load or condition is included in the fault code this can be an advantage during diagnosis. Normally a code set during idle or light load is relating to an air leak. And a code set during high or part load can be a fuelling issue or an erroneous sensor signal.

Read more: https://www.autocodes.com/p0175_mercedes-benz.html

As for loosing oil, my guess is that you have a broken gasket on the intake side somewhere, sucking in oil and that may be the cause of your rich engine. All a guess of course as there could be be other causes, PCV valve circuit, etc

bhpplease

Thanks Sunnyslope48.

I have been doing some more reading on this. The car currently has 0w30 which is low viscosity by any definition people have reported similar issues on long motorway drives. The car is also getting on in miles at 194k miles.

So, I need to drive back after the holidays soon and do the same trip as what triggered this post.

I have decided to run an experiment and change the oil to 5w-40 for the return trip (400 odd miles). This should serve as a pretty reliable to test to eliminate that question and see if any oil is burned.

You see, I don't do many long trips at all really and I could spend the next 6 months wondering if I don't use this time now.

What do you guys think?

Some of you might comment regarding short trips and higher viscosity oils. Here in London, England the weather isn't too cold, so I think 5w-xx should be ok.