Hello. I have a 1986 190D with about 180K on it. Ever since I moved to a more dense area, I have been driving very little. I changed the oil and fired the car up after about 2 months of sitting and have noticed my engine is very loud. This doesn't sound like injector nailing to me, but valve noise. If I was working on a car with adjustable valves, this would be the first thing I would check. It's very loud, and very consistent only changing with engine speed. It doesn't change much or at all once the car is warmed up. I'm mostly sure its not the vacuum pump (thankfully). Is it possible my lack of driving has caused some lifters to collapse? I have no problem swapping them all out, I'm just looking for a starting point. I have cracked all of the fuel lines individually with no affect. The are no other symptoms. idle is smooth and there is no smoke or lack of power. Thank you for any suggestions. I'll try to post a video or sound clip.