Lucky Criminal

Hello. I drive a 2007 CLS 550. Recently I plugged in my scan tool. It's not perfect, but it was able to communicate with the majority of systems. Out of curiosity, I decided to look at some live data and parameters from the screenshots appeared.




Can somebody tell me what is going on? Everything's in the specified value range, there's no DTC or check-engine light. However, values on the exhaust side are more extreme and differing than on the intake side. Is this a sign that I'm starting to have problems with valve timing? Do you think it's urgent? On idle I can hear clatter, like in old Mercedes diesel (W123/W124). It has been like that for a year now (mileage around 1800km/1118 miles). I think it's neither better, nor worse. What's causing it? Worn out idler gear? Stretched timing chain? Worn out camshaft adjuster? I looked under the cap during oil refill- looks fine to me (unless the visible parts are something completely different). Any ideas?

M273

Unfortunately, your model is subject to a chewed out idler gear, located behind the timing case, close to the centre of the engine.

You have, likely, a change in the timing of the left bank cams as a result.
It's a front of engine off job to fix it. You require some particular sockets and drives, but nothing too hectic.
I would also replace the tensioner guide, it's the only one you can change without removing heads, the oil level sensor o ring and the dipstick tube seal. They're a ***** to get at otherwise. I used a slide hammer (attach to 2 bolts on the cover at least) to remove the cover and the chain guide locating pin. My pin was very tight, it took dozens of taps to free it.
But before you dive in, there is a tutorial from yilmaz.tv on the tube that shows how to mechanically diagnose before you pull your car into several dozen pieces. I've also posted a couple of tips here as well.

Lucky Criminal

Thanks! I'll check it out. According to MB my engine should be free of that fault (Serial No. 182924), but I don't believe them.