1985 500SEL Starts great but idles around 1100-1500 RPM (used to idle about 800) Some times it's about 800 and some times it is arround 2000 nut it is usually between 1100-1500 and I can't pin down any sort of pattern. I am not sure if this is a related issue or not but the Economy gague on the dash is always in the red evev when idleing near 800. any ideas? I did not buy this car to save gas but with gas prices the way they are I can aford for it to be burning more gas then it is suposed to.

You have a vacuum leak or a leak of the piping which comprises the idle air system. It could also be an idle air control valve stuck open. Your car should idle at 650± 50 or thereabouts. Even 800 is a little high. Get it looked at soon since slamming the car into gear at 1100-2000 RPM will land up costing you much more in transmission repairs than correcting this relatively minor issue.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Thanks for the quick reply,

I love to work on this car myself, do you have any advise or have you seea thread that will help me check this out? I saw an article in DIY that describes how to check for leaks in the vaccum system. Does this apply to my issue.

Thanks

the air cleaner and with the engine running spray wd40 on all the vac lines. when you are near the leak the engine will speed up.

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.

That sounds simple enough, I will give it try tomorrow morning and see what I can find. I guess the fix is to just replace the leaking line?

the rubber fitting.

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.