I have an 88 300E w/ 200k miles. The idle has been quite rough for about a month now. It will happen when the car is stopped regardless of gear (P,R,D) after it warms up. The car will shake and from the outside you can see the muffler shaking. The rpm's won't move much and will stay around 5. The oil pressure will move between 0 and 1 1/2. The fuel economy will move half way towards the red and will move a bit in both directions along with the oil pressure. Once I give it gas and the rpm's go above 1 it runs fine. I have been getting about 16 mpg since this started. It has new plugs, wires, and filters. Can you suggest something before I take it to a mechanic.
Thanks a lot for any help