I replaced the idle control valve (because of high idle), including new rubber parts. I did nothing else. Now, attempting to start, it cranks, sputters a little bit, but will not start. What could have gone wrong? Adding to the mystery is that, immediately after the replacement, with the rubber hoses still the old ones, I got it to start, but it ran at a very low idle RPM (200 or so). I figured that problem could be because of the old rubber parts leaking, and that's why I replaced them, too. But no.

I tested the valve with 12 V. It sounds like it works.

As far as I can see, the polarity of the wires going to the valve does not matter, or does it?

Hannu, MA

 

Had a similar problem in the other day, try swapping wires, is there a feed to the unit, maybe a broken wire (internal) is the unit on the right way round?
The one i had in had an air pipe that had been disturbed & was leaking to atmosphere so check all air & vac pipes in the area.
Have fun!

 

Problem solved: MercedesShop sold me the wrong valve!