Well, I have a 300D with the 2.5 turbo diesel engine, and it has roughly 240,000 miles. It has a few issues and I hope to learn more about this car and what's wrong with it.

It's got a really rough idle. When I start it in the morning, it idles fine for 30 seconds or so. After 30 seconds, it starts smoking and shaking. I think it must be misfiring, it produces a heavy white smoke screen out of the exhaust. (I'm going to update this and provide a video clip tomorrow.)(Video: https://my.mixtape.moe/mixdke.mp4). When I start moving, the car is very jerky and it chugs at the lower rpms until it builds boost. After the car warms up, it idles better. (Above 50°C)

After 5 minutes of driving, the turbo stops spooling and building boost entirely. I can tell this from the power output and sound of the car. Very slow acceleration, difficult to reach highway speeds while merging. The vacuum lines under the hood are in pretty bad condition. I've noticed cracks in the rubber, I think they're dry rotted. If someone can provide info on what size I need to replace all of them, I'd appreciate it.

It's also leaking coolant. When I park it on an incline, I notice the coolant level goes down and there's coolant on the concrete. I think I may have found a leak on the return line to the resovior.

Hopefully someone can help me understand what is going on. The car does have paperwork for all the maintenance done, I'm going to take a look at it tomorrow.
Thanks

What's the smoke smell like?

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

It's a heavy diesel odor, smells pretty strong.

Check your fuel filters and see what kind of fuels in there. It's worth seeing if they're clogged up. You'll get a good idea from looking at the pre-filter as well but the main filter is a tell-all.

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

At what RPM are you idling when hot and cold?

It's right around 600-750 hot and cold. I don't know what this would mean.

750 is normal cold. 600 is normal when its warm. Nothing out of the ordinary.

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Could be a source of the problem.

Did you check the fuel filters?

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Been a little busy, I'm going to do it this weekend.

A simple test I might preform. Feed a constant voltage to the glow plugs.


If the engine does not roughen up after the thirty seconds that way. I would do a compression check.