Air Cleaner Plug
 

I happened to notice my air cleaner was missing the little round plug near the center (see photo), so I picked one up at PartsShop.

Then I started wondering -- what's the purpose of the plug? I assume it's always supposed to be attached, as dirty air could be sucked in otherwise? Have horrible things happened to my car from this plug being missing (presumably for years?)

Is it an access hole for an adjustment tool or something?

It is an access hole for an adjustment - do a search on lambda and read all about it.

Thanks, I recall reading about Lambda, I'll make sure I keep that plug in to avoid temptation. :) Hopefully it didn't suck in any of the old deteriorating hoodliner in the time it was missing.

Kind of aggravating that my MB dealer didn't catch this (or horribly dry cracked ignition wires) at my 90K service... both seem pretty obvious. :(

I noticed the same plug missing on my 300E. It plugs the access hole for a fuel inj. adjuster. On my car the adjuster hole had a metal plug in it so it wasn't accessible anyhow. I understand the plug can be easily removed to get at the adjuster, but you should know what you're doing before you fiddle with it.

Gary