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"Gretchen" my 1986 300E 286000 km+ (RIP) August 2015
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Discussion Starter · #1 ·
I own a 1986 300e 3.0 118K. What should my idle be at while in neutral or park. I'm presently running 8 and it seems rather high. Any suggestion and if so what would I need to do to lower it. Thank you
 

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1991 Mercedes 300E
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should be around 750. not ttoo too bad, but get the dealer to run some tests. throdel body, air idel control, possibley a vacume leak. also what fuel r u running, ment to run on premium, remember that.
 

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"Gretchen" my 1986 300E 286000 km+ (RIP) August 2015
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Discussion Starter · #3 ·
Thanks for the reply, actually found a vaccuum leak, cracked hose. Adjusted the idle/rich using multimeter, on the duty cycle setting to 45-50% runs like a new car
 

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89 300E
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Could you share with us more details?

Which hose got cracked? Tell us more about using the multimeter to adjust the mixture. Any web-links to info about this?
 

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"Gretchen" my 1986 300E 286000 km+ (RIP) August 2015
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Discussion Starter · #5 ·
Actually I was checking all vacuum hoses and found a crack one, I can not ID for you though. As far as the adjustment is concerned, this was previously posted by member Yal. ( Thanks Yal !!) Do an additional search under idle mixture or fuel distributor adjustment and you should be good to go. This forum is a great source for maintaining and trouble shooting

Its pretty simple. Now it may not be the cause of your problem but its a good start. What you need however is a multimeter from sears that reads duty cycle as a %. Real cheap cost about $30-40, and invaluable http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=03482139000. Then you need a set of allen keys, I believe the adjustment nut is #3 allen size but I am not sure, I just bought a set of them. Take of your air cleaner and you'll see a "steel" tower next to the fuel distributor. The adjustment nut is located inside at the bottom of that tower. Now you have to locate the x11 connector on the driver side fire wall. Its basically a round socket. It looks like something should be plugged into it. Its usually covered with a plastic screw cap.
With the car running and warmed up and your mutimeter set to duty cycle stick the positive terminal into the number 3 hole of the x11 connector and ground the negative terminal. I usually stick the negative on a strut support bolt next to the driver side hood hinge.
Then watch the duty cycle. If its not swinging back and forth make sure you selected % by pressing one of the selectors at the top of the multimeter (took me forever to figure this out).
The duty cycle should fluctuate around 50%, if it doesn't you have to adjust the screw at the bottom of the tower until it does. If I remember correctly clockwise brings it up and anti clockwise vice versa. Adjust by small increments and wait 10 seconds each time. The screw is spring loaded and so you have to depress it a little to get it to engage before turning. If you depress it to far the car will cut off.
Thats it.
It could turn out that all you need is a fuel filter change

If you do this let me know what you find. You can check the same thing from the EHA which is a little balck box at the back of the fuel distributer but you need a test harness for this.
 
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