OK OK sorry to start a new thread. just delete it after I bought this car. (or not)
I checked out an '83 SD, silver, blue inside, no sunroof, interieur nice but driversseat ripped at the spot where you touch it when you get in, 167000 miles, odo tach clock windows air gauges everything works. doorlock dr side jammed. vacuum ok though. one key. not many dings, paint needs buffing or repainting if you are precize. no rust at all. car has been in storage 2 years.
engine looks new. as in, all the copper is new looking, the aluminium too, it just looks like a 70000 engine. little greasy oilpan, nothing major.
the only thing is:
it IDLES REALLY BAD! 5000 rpm and the whole car shakes of it. it shook the engine mounts to pulp. over 1000 rpm it's a lot more quiet. normal, yet loud. it looks like they did something with injector 3, the aluminium around it on the valve cover gasket shows scratches. I drove it and it has bad pickup but goes over 85. otherwise fine. WHAT IS THIS?? diesel gone bad from storage?

5k rpm.. it shouldnt idle that high or even run that high... post a thread asking for a carfax on that car with the vin handy.. it will tell you much

i could be alot of things, injectors, lack of valve adjustments,filters, ect. should you decide to buy it, change filters,adjust valves and run some dp through it.

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have no worries.....President Obama swears "If you like your gun, you can keep it

Do a compression check (if the owner will allow). If it checks out OK, I say buy it.

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1976 BMW 2002- 100k
1995 BMW 325i 175k
1984 Mercedes Benz 300D Turbo Diesel- 270,000 mi

1981 Mercedes Benz 240D- Estimated 300,000+ mi Returned to the earth

sorry I meant 500rpm (too low I know), I have no vin (I can get it though seller seems honest. for a seller.) and what is IP?)
I'm thinking about taking the risk I got him down from 3500 to 2200. if it's something simple like a flush or 500 miles flooring the car on B100 I would be pretty happy.
if a cylinder is ****ed i would not
a compression test, is that easy to perform by your 'random car sales smithville' ?? or maybe slightly special diesel?

I agree, you should get it checked out before you make an offer. The spec for idle speed is around 700 rpm, if I recall. I can get mine to idle smoothly down to about 550 rpm, but everything has to be perfect. There are several potential causes for the rough/slow idle, and there is no way of determining what's going on with out having it inspected. It's worth a couple of $100 to have it checked out if you are seriously considering it.

You really should try to find an independent benz shop in your area. I doubt you will get a good inspection by a general mechanic, because they don't know what to look for. BTW, a IP is an injection pump (the main fuel pump with the metal lines running to the fuel injectors.