I am having a problem with my 500SEL. It does not want to start. Before it stopped running I would sit at a light and the idle would start lowering and I would put it in nuetral and the idle would go fast, this would stop it from stalling. I have heard it could be a few different things... a vacuum leak, a fuel filter, a fuel pump, a idle sensor... I am at the point to pull out my hair I am a diy'er so if I could get anyone to send me a comment/help please help thank you all is appreciated.

Since you just posted this, I am going to hope that you are perusing the archives and searching for some answers.

Vacuum leaks, are no different than on other cars....Look at all of the tubing, check for cracks, replace when in doubt.

Same with the fuel pump....it's electric...it's either hissing or it's not. Fuel filter is either filtering, or it's clogged. If you don't know when/if it was replaced, it's not going to hurt the car to replace it.

I think on your engine there is a idle control valve towards the front left of the engine. I have read that these can get groady and that cleaning them has done good things. Might wanna search for that gadget on this site first.

Good luck.

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

I think your's has a base idle screw....?
Plastic screw in front of drivers side air idle hoses.
Points straight up, slotted, centered....slightly towards the drivers side cam chain hump.

If so, adjust .
Good idea to replace fuel filter too as suggested....
Next would be to check the ignition timing....10 before or so, idle.
Mechanical advance dizzies get sticky and hang up, need lub and checking for proper advance curve.

Rest of things would be....O2/Spark plugs/Wires/Dizzy cap/Rotor/.........
and then cam timing.


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"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."

batch of fuel?

i would recommend against adjusting the idle. it is prob not the prob and if you fool around with adjustments then if and when you fix the main problem you will be all out of whack.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

This thread is really interesting to be because I am seriously considering the purchase of a 1984 500SEL. I will know for sure when I look at it on Friday afternoon. The reason why it is so interesting is because I was also considering a 1985 500SEL that has a very similar problem that you are describing your 84' has. Hopefully this is not a trend on the 84-85 500SEL. I know that problems vary from car to car, but these are two of that I know of with the problem and it is not like these cars are all over. Luckily, as far as I know, the 84' I am considering is supposed to be in perfect running order, so hopefully that is really the case and it will stay that way for a while.

Good luck to you and keep us posted.