Letting of the accelerator pedal on my 300D does not slow the car down very fast. The engine takes it's time slowing down, especially at highway speeds. Other than that it runs good. I made two long trips in a row totaling 480 miles and it used 1/8 of a quart of oil. Any ideas?

Linkage needs examined from the pedal to the injection pump. May just be sticky or the return spring is weak or even missing I suppose.

There's not much braking from the engine in a diesel and certainly not the same as a gasser. Could you be comparing the two?

Actually on a straight stretch the speed drop should be very noticeable. Taking your foot off the accelerator should cut fuel to the engine back to idle immediately.

If not then your linkage is binding on its way back to idle position. You need to start by lubing the ball sockets and other moving parts with ATF. If that doesn't improve the situation, then something is missing from the linkage or it's been messed with.

If the linkage sticks open in slower traffic situations, it can be dangerous (voice of experience).

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

My experience has been the exact opposite.. my diesel engine-brakes more significantly than the gassers. I always assumed it was because the diesel engine had higher pumping losses when in this situation than the gassers, but maybe its just some tuning (or mistuning) on the engines/transmissions.

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

Since the diesel engine doesn't have a throttle the pumping losses at any given engine speed and displacement should be less. However, W123 diesels generally have fairly short gearing and no overdrive, so the available engine braking in top gear is more than you'll experience in most modern gassers.

I second (third?) the sticking/binding linkage idea.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

Disconnecting the linkage from the IP and manually reving up, it takes a while for the RPM's to drop.