I have an 85' 300 diesel, non-turbo. It has 204,745mi on it as of today. I change my oil (have always used Mobil 1 full synthetic)every 3000mi with filter, and air filter every 6000. The fuel filters are <1000mi old.

My question is: Lately the engine will begin to lope (idle roughly) after extended driving (over 10mi) when the engine is at full operating temperature. Please note that idle speed does not affect the problem, as in this car there is a knob on the dash that controls idle speed. This problem is troublesome as it causes the car to shake while idling in gear. So far it has never stalled. What would cause this problem? I am confused because there is no problem when the engine is cool regardless of engine speed.

Could it be the injectors, the fuel pump, the fuel pump start-of-delivery adjustment, or transmission related? Also, I thought it could be something to do with the timing chain, as it could expand as the engine warms up. Please let me know if any of these could be the cause, or if I neglected some possibility.

TIA
Dr. Adam T. L. Delecki

I am guessing your car is a Euro car, and i have seen euro 617 engines without this adjustment, so take a look..

There is a bolt on the back side of the injection pump with a locknut, loosen the locknut while holding the bolt, an tighten the nut until the engine stops shaking, then tighten the locknut.

John

Thanks, I'll thry this, but after I mark exactly where it is now.

Dr. Adam T. L. Delecki

If the roughness goes away just as soon as you tough the accelerator, the dampening spring on the rack in the injection pump has gone bad. This can be adjusted some, but usually requires replacement to completely fix.

Its usually not worth it unless something else needs to be done. I think the spring can be replaced without removing the injection pump, but I'm not sure. If the pump has to be taken apart, you might just want to endure it until the engine needs a rebuild, and take care of it then.

Also, you may have bad injectors. Not very expensive, about $50 each plus the seal. Usually aren't shot at 200,000, but a possibility. Usually worse cold, though, than hot. Try running a bottle of RedLine in you next tank of fuel (the whole bottle in a full tank!). If the problem goes away, then slowly comes back, the injectors need to be looked at.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks for the advice. I'll try adjusting the pump; Do you know how to replace the spring for the dampener or how much it costs (part #)? I would appreciate any advice, as my Haynes manual touches little on the workings of the fuel pump.

TIA
Dr. Adam T. L. Delecki

I had a rough idle after heating in my 601 engine. While different than your engine, my problem turned out to be a stretched timing chain and a less than perfect tensioner. As a result, as the car heated up, the expansion in the chain and the failure of the tensioner was enough to alter the timing a little bit so as to cause rough running. When I replaced these two (along with all of the rails which were gouged due to the slop), it ran perfect again. This was over 100kmi ago, and I have not had a repeat problem.

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Jovan

'84 (11/83) 190D 2.2 5-Speed; Silver/Blue; Motor No. 00354, 402k mi (340+kmi mine)

'89 Porsche 911 Turbo Coupe; Black/Black; 53kmi
'05 BMW 530i 6-Speed; 302kmi
'19 Range Rover; 30kmi

Dr. Delecki:

Sorry, I've never done this. There are others who have, you might want to search this site for specifics, I know I saw a description somewhere. Otherwise, you need to find someone who has previously performed this repair, the Haynes manual is useless for IP internals.

Jovan:

I wish a new chain would fix my 603! Unfortunately, #4 knocks like crazy and is low on compression, too -- #2 and #3 are weak, too, and compression is marginal. No way a bad chain will do that!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!