Lately I have noticed that when my 84 300sd idles in park, the idle speed flucuates. It speeds up then slows down, over and over. Lets say 800 to 900 rpm and back. You can just see it on the tach. Stops if you place the car in drive.

Where should I look?

Can you hear the engine change speed or is it just in the tach? I have read that a lot of problems with the tach come from the tach amplifier mounted on the driver's side inner fender.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

The engine speed is actually pulsing up and down.

That's odd. How old are your fuel and air filters?

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

The idle governor pin (rack dampener bolt) needs to be adjusted. Mine did the same, adjustment of the pin removed the pulsing.

IIRC, if the pin is adjusted too tight, pulsing will happen. Adjust it back out a little.

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http://farm8.staticflickr.com/7271/7...144c3fc1dc.jpg

Idle dampener on the end of the IP maybe? There is a screw there to adjust idle and a spring in the cover. If the spring wears out, it could account for a lopey idle.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

MBeige beat me to it.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Lopey idle is the perfect description. I will try adjusting the damper adjustment tonight.

Thanks so much for the suggestions.

My '85 300d will have a slight pulse/lope at idle occasionally. It's more visible in the oil pressure gauge than the tach, and goes away when in gear.Haven't tested for any consistent variables because of the infrequency.

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1985 300D-189k The 'UD', Ivory and Pinkamino
1979 300D-211k Dark Gray, Parchment
A 1980 Harley-~166k and
A 1994 Ford diesel pickup-349k and
A 1990 gasser Volvo wagon-145k

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