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I've been reading this forum for a few years now, and am super thankful for all the knowledge that I was able to pick up here from the members. Today I came across something that I was not able to solve by just searching around the forum and the web, so here is my first post on MBWorld.
I am currently in the process of replacing the crankshaft ventilation hoses and the valve, because I figured that for the symptoms I got (P0171 error code, unstable idle, oil leak from that side of the engine, bad fuel economy) that's the most likely cause. I am using Slammer111's excellent write-up as a reference, and will report there once I'm done
So while I was removing the intake manifold, I've noticed that there is a hose, which looks like a vacuum hose that comes off the throttle body and goes nowhere. I guess it was detached, because nothing else in the car is just hanging loose, I mean everything is neatly zip-tied and clamped and so on. On a closer inspection, I found what I think is the second part where the hose attaches. It is some kind of narrow white hose behind the window cleaner tank. Looking at the pictures and video online I was able to confirm that my hose indeed should be connected to the white hose, although mine is behind the washer tank, and there it was in front (does not matter perhaps?).
This does not look like any heavy duty line, it does not even have a clamp - or maybe it got lost? - but it goes to the throttle, and I was wondering about its purpose. Could it cause the unstable RPM 500-1800 at idle for example?
My car is 2003 C230K, M271, manual transmission. The detached hose Here is where it is connected to the throttle body And I guess this is a corresponding white hose?
The thin rubber lines are part of the secondary injection section that allow a bit of exhaust air from the EGR back into the intake. There's a thread around here somewhere with a M271 diagram where I posted the line lengths.
I also have the same weird line that goes into the tube. Never looked into where it went. Mine doesn't have a clamp either. While you're in there, any chance you can poke around see where the white tube goes? I'm a bit curious too.
Last edited by slammer111; May 7, 2025 at 03:00 AM.
Thanks for the reply! Absolutely, I'll poke around. Not sure how much I'll find out, but since I don't have any pressure to complete the job fast I'm thinking why not.
And hey, thanks for the link. I read this article that you linked, and after that googled some more to clarify things, so now I'm feeling more knowledgeable. IMO it's a good idea to know more (rather than less) about the engine one is working on.
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What is this vacuum line?
