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Old 12-07-2011, 03:03 PM
ChiefRider ChiefRider is offline
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Join Date: Dec 2011
Location: North West CT
Posts: 378
Intro and First Question: Engine Starts Smooth, then Runs Rough


Longtime Benz owner, and for better or worse I find myself a Diesel owner again. I started out with a '79 240D 4 speed. While it was a low mileage car, it hadn't had it's oil changed as frequently as it should have, and had a bit too much blowby. In spite of this, I ran the wheels off of it until I didn't need it anymore. After storing it for a couple of years, I sold it to kid who bought it sight unseen, taking a bus here from 3 states away. He arrived with a plate, and left directly to Colorado. He made it, too!

A 300E, E430 and 560SL have all been mine to enjoy since then. Times change and now I have a 1991 350SD. I know this is noone's favorite engine, but it's what I have, and hope to get some use out of!

Here's the situation. The car has 205k miles, and is in outstanding condition. The PO "rebuilt" the engine 40k miles ago. The rebuild consisted of a new cylinder head, a reground crank, 2 new connecting rods and all new rings. He claimed at that time the cylinders still showed crosshatch and checked out fine. Oil changes always at 3k miles.

Here is what I am experiencing. The engine (reportedly) consumes no lubricating oil. Without getting into it, I trust the owner's testimony on that. The engine starts easily and instantly from dead cold, and runs perfectly smooth and smoke free for 10 seconds or so. After this time, it begins to skip and shake, idling quite rough, and puts out a pretty fair amount of whiteish bluish smoke. Car has low power, but is driveable and the engine gets smoother under load- I can do 70 on the highway without any trouble. Occasionally power seems to come up, engine smooths out even more, but then will lose power again.

My indie has "cracked" the injectors loose one at a time and run the car. Only 3 cylinders significantly affect the running during this test; the other 3 didn't make any difference. He deemed this inconclusive.

These symptoms are pretty confusing to me. Anyone with a similar experience and cure?

Thanks much!

1991 350SD

Last edited by ChiefRider; 12-07-2011 at 03:17 PM.
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