My Haynes manual says that this switch must be engaged when the accelerator is in the idle position, can anyone explain exactly what this switch does? Also here`s a very helpfull tip for the do it your selfers. The best Merc guru in Australia gave me one of his Lamda tunning secrects. You need a volt meter, stick the positive prob into pin 3 of the diognostic scocket and the negative probe to battery minus, at idle (warmed up no accesories running) adjust the allen key mixture screw in the hole through the air cleaner(you must press down on this screw because it`s spring loaded) the best reading is 6.8v to 7.2v. clockwise is rich (over7.2V)and anti clockwise is lean(below 6.8v). the adjustments are easier to make with the engine switched off as when you press agaisnt the spring loading the engine will choke to a stop. do it a little at a time until you get to the 7.2v at idle. Mercedes charges like a wounded bull for this because they hook up that diognostic computer to do the same thing. ps get to that 7.2v and you`ll have a perfect smooth idle.

[Edited by georgehifi on 07-15-2001 at 05:18 PM]

Does`nt any one know what this micro switch does!

It's to reduce emissions on deceleration. It allows computer to equalize the fuel pressures.

M.B.Doc thanks, so it kinda like stops the injectors from spraying so much on like down hill coasting and such? What do you think of the simple Lamda setting using a volt meter, seamed to work very well for me, is it a good diy tweak on the cheap?