'87 190D 2.5T "Bucking" when cold.

[Jetmugg]

My '87 190d 2.5 Turbo (5-speed car) has a problem with part throttle "bucking" when the engine is cold. This is not just in cold temperatures, but during the first few minutes of operation (even in warmer weather).

Under part throttle conditions, (in gear) it's a fairly violent on/off/on/off/on/off bucking of the engine. If I mash the throttle pedal, the condition is minimized. After driving the first mile or so, the condition is totally gone.

Any ideas on this one? The fuel filters are fresh. Engine has 242K miles, about 10K of which have been put on by me. Since I got the car, this condition has always existed.

SteveM.

[quattro]

Originally Posted by Jetmugg

My '87 190d 2.5 Turbo (5-speed car) has a problem with part throttle "bucking" when the engine is cold. This is not just in cold temperatures, but during the first few minutes of operation (even in warmer weather).

Just finished my 5 speed conversion and I have the same problem. Going from 1st to second it's almost like someone was playing with the throttle opening and closing rapidly. Problem was not there with an auto tranny and with manual goes away after engine warms up a bit.
Did you ever figure out what caused it? I am hoping it's as easy as a bad tranny mount allowing the drivetrain to move back/forth.

THanks for suggestions.

[Diesel911]

Any chance you are having an air leak?
If not other fuel inlet problems with filters ect or EGR problems (if you have one disconnect it and see if it helps) I would be thinking IP timing.

[2.5Turbo]

If these have the same type of overboost protection as the other 87 diesels, you may want to check your overboost switchover valve, switch and wiring. Also check the wastegate hose to make sure you aren't legitimately overboosting.

[beaulieub]

I'm wondering if this is the same problem I'm noticing on my new-to-me 87 300D. Engine shakes violently when cold if I get out on a high speed road (50MPH+). If I take the road into town (max speed 30MPH) no shake.