joachimweiss1

Mercedes S Klasse Diesel Engine Trouble

My 2009 Mercedes S Klasse diesel is throwing some seriously weird codes. I'm getting fluctuating cylinder pressures, higher fuel consumption than usual, and a noticeable drop in engine power. The car has about 143333 km on it. I've checked the usual suspects, or at least, what I thought were the usual suspects. I was worried about the head gasket or maybe even something with the camshaft. I also took a look at the turbocharger and the intake manifold, but everything seems normal. Could it be something with the timing belt? Any ideas before I tear what's left of my hair out?

4 comment(s)

That sounds frustrating indeed. I recall battling similar gremlins a while back with my old Audi A6 TDI. It drove me absolutely bonkers! I experienced similar symptoms. Have you scanned for all possible fault codes? A seemingly unrelated sensor malfunction elsewhere in the system could be causing the cylinder pressure issue as a consequential error. Is the engine running rough, or is it primarily a power loss issue? Any unusual noises, such as ticking or knocking? Also, are you observing any smoke from the exhaust? What are the exact fault codes you are getting?

Thanks for the reply! Yes, I did scan for fault codes and that's where I saw the 'cylinder pressure fluctuation' error along with 'reduced engine power'. It runs slightly rougher at idle. No unusual smoke from the exhaust, though. You mentioned a seemingly unrelated sensor malfunction. Any specific sensors I should be focusing on? And what was the final resolution for your Audi? Was it a sensor issue causing a cascade of problems?

In my case, the Audi saga ended with a faulty MAF sensor. It was reporting incorrect airflow, which threw off the fuel mixture and caused all sorts of havoc, including cylinder imbalance and reduced power. I would begin with the sensors related to the air intake and fuel delivery system. But, I must insist, these Mercedes are complex beasts. It would be best to visit a workshop. This is very likely to be the result of a defective sensor.

You are a lifesaver! Took your advice and brought it to the workshop. Guess what? It was a faulty sensor in the exhaust system causing all the chaos. The repair was covered by insurance, so it literally cost me 0€. Thanks again for your help!

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