When I start it, it idles fine.
After I run it, when I put it in park, the engine revs incredibly high- makes me shut the engine off pronto as to avoid any damage- not sure how high it will rev 'cause I haven't let it get that high before shutting it down.

Your input would be greatly appreciated.
Thanks in advance.
Jay

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Wordmanjay
Tribetown, Ohio

A couple of questions first; Is this car new to you? If so, has it done this since you acquired it?
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If not new to you, Is this something that just started recently?

Have you performed ANY type of service to the engine, as in have you physically touched, turned, or pushed anything prior, to, or after this started happening?

How many miles on the engine?

#2 diesel only?

What are the last three service items done on the car?





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ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

Some other items

Linkages sticking.

Over adjustment of the Rack Dampener Bolt/Screw can do funny things.

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84 300D, 82 Volvo 244Gl Diesel

Completely new car to me. I haven't done a thing.
It is rigged to run on veggie.

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Wordmanjay
Tribetown, Ohio

First step would be to determine if the problem is internal to the IP or in the linkage. Have someone start the car and you hold the linkage so it can't move. If the linkage is in the idle position and it keeps revving, the problem is not the linkage. Has the shut off valve been replaced recently?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

All the comments so far are good things to check / verify.

Given that this is a new car to you, if after you have verified that the linkage is not hanging up, I would recommend the next thing to try, as the other member mentioned, is to back off the Vertical Throttle Stop about / at least, 4 turns and see if that stops the worm engine revving. The Vertical Throttle Stop is vertical screw with a lock nut, that is located between the engine and the IP and is what the throttle lever contacts when the throttle is in the Idle position.

If the Idle Governor, (an internal setting), is not set properly, as is the case for 240Ds, the Idle Governor Spring does not have enough tension to maintain a strong idle when the engine is cold, and the first thing everyone does to raise the idle is to turn in the Vertical Throttle Stop, increasing the Throttle input, in an effort to strengthen the cold Idle.

The problem with using the throttle to maintain an Idle speed is the throttle does not modulate. Because the throttle is now, pushing on the flyweights in addition to the Idle Governor, (helping the Idle governor), any change, or regulation of speed, must be a collaborative effort, however the Throttle does not modulate, so when the Idle speed starts to exceed the regulated range, the Idle governor will try to reduce the speed, but the Throttle will hold it from dropping enough to reduce the idle to the desired speed. When it is cold, the engine needs a touch more fuel to idle, but when the engine is worm, that same amount of fuel will cause the engine to rev up.

If the Idle Governor is set properly, you should be able to back off the Vertical Throttle Stop at least 5 full turns and the idle speed should not change very much. What should change is how quickly the engine returns to idle when it is revved up.

If, the idle speed is DEPENDENT on the throttle, then the Idle Governor spring tension needs to be increased so it is strong enough to regulate the idle speed in both warm and cold conditions. The problem is, the Idle Governor Spring Tension screw is inside the governor, behind the back cover, and the setting is easy to mess up.

First things first. Fingers crossed.