I just picked up a 1979 240D with 215K from Byrdandcompany here on the board (he's local to me, and it turned out our wives know each other). Its a great car for its age, and the body is in especially good shape except for the paint. I had driven it a couple times and not had any issue with idle or running. A couple of days ago it developed a definite nailing issue at idle. It nails some (sounds like on the #1 cylinder) and the idle drops a little when it starts nailing making the whole idle a little erratic. If I twist the fast idle ever so slightly so as to add about 100 rpms (if that much) the nailing and erratic idle go away completely. This car was sold to Byrdandcompany by our local MB indie Dietmar (West Memphis FCS). It had been owned by an 80 year old lady and hadn't been used much in the last couple years. Should I give it a chance to clean out on its own, maybe run a little Biodiesel through it (have a local source for it since this is farming country), or should I go ahead and pull the injector and check it out? Dietmar had checked the car out thoroughly and I believe he serviced the automatic transmission as the fluid is clean and the shifting points are clean without any jerk or surge. This is no doubt the best running 240D I've been behind the wheel of - it is slow off the line but really picks the steam up after 35mph (my last one was an '83 with a 4-speed manual, and I swear it didn't have as much pep as this one). The interior is in good shape on this one, and all of the power windows work except one, and the sunroof even works!