87 300SDL

This winter I was highly annoyed at my Benz for taking soooo long to warm up to a smooth idle, took it into the shop even, which was a waste of $600 and no resolution.

Basically by Summer I figured this would be long gone, but it takes a good 10 minutes of driving to get rid of the rough idle.

I don't know where to start. Even after the coolant is up to full temp it still has rough idle. I just ran some Diesel Purge thru with no real affect. I'm guessing this is an injector issue?

Where do I start?

Thanks for any pointers,
Bill

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'87 300SDL, intensely modified Greasecar setup, with nickle plated heat exchanger, 3 valve setup, 312,000 miles
'95 Suburban diesel, Greasecar basics, 16 plate heat exchanger, mercedes fuel lines, Racor filter
'85 Renault Alliance converted full electric vehicle