This is on my '79 240D

The IP sometimes sticks open. I have gone over the throttle linkages several times, and made adjustments to try to shorten the length when the accelerator pedal is not pressed, but if I take it too far, I can't get to WOT when it is pressed.

The problem is most apparent when I use the clutch to move into neutral while the car is at mid- to high rpm

Today, I parked in the driveway and played with it while the car was running.

I manually revved the engine. The throttle linkages snapped right to where they should when I let go, but the engine response lagged behind by about 1 sec or so.

It did go down, but while driving can stay high, and sometimes at idle even creep upwards.

Does anyone have any troubleshooting ideas?

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Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

Maybe your idle speed is set too high? If it idles above a certain speed the pump's internal governor can lose control and let the engine rev up. On a 240D you should have a manual idle adjuster on the dash -- make sure you're adjusting it to the lowest setting after the engine has warmed up.

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1981 Mercedes 300TD, 1994 Honda Civic Del Sol
http://mefi.us/images/fuelly/smallsig-us/67195.pnghttp://mefi.us/images/fuelly/smallsig-us/103885.png

sound like the idle adjustment, the vertical one on the outside is adjusted to high. This will change the idle speed slightly, but it mostly effects how fast the engine returns to idle. Loosen the nut(9/16 deep socket) and then turn the screw anti clockwise in one turn increments each time revving the engine and seeing how well it returns to idle. Once you have it where you like test drive and see if it needs any more fine tuning. Fine tuning should be done in smaller increments. Don't forget the tighten the lock nut when done.

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1977 240D turbo

Thanks, this did the trick. Still some fine tuning to do (drops a bit too fast now), but this was the issue.

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT