1985 Mercedes Benz 300td Two Wheel Drive Automatic 168000 miles

Hello.

My turbo diesel is a strong running car with relatively low miles. Just last week I was on the highway cruising at 75 near 3200 RPM's. I felt a studder in the gas and a choking feeling as the car was not receiving fuel. The car began to slow down and putter but then it sped up again and regained normal functioning. I thought perhaps bad diesel and filled her up. The car ran fine for a week and is now doing the same thing. The car stalled twice but has not completely broken down. When I put the car in neutral I have no problem getting rpms. I drove to work this morning and the same thing happened. I dont understand why this is happening. Can you offer some advice?