I just bought a 1980 280ce which has a very rough idle. I took the car in to get a tune up thinking it was a bad spark plug (not my usual import mechanic, however he is a trusted mechanic who works on my 65 mustang), and he said i probably had an intake leak somewhere and that it may be a bad gasket. He sprayed a little carb spray on the rear of the block and the car settled down nicely afterwhich a few minutes it went to a rough idle again. The car does not smoke at all and has a relatively low 130,000 miles on it. He changed the oil and reported it was all oil. I was just wondering if anyone can offer any insight or suggestions.

Sounds like a leaking manifold gasket? or a vacuum line. Usually whenever I have idle problems in MB's it is related to a leak of some kind. Your mechanic is correct in locating the leak, some people spray things around the hoses and connections to determine where the leak is, you can also spray around the joints of the gaskets. My guess would be the fuel injector seals first. I think that model is fuel injected. That little 280 motor in there is a wonderful engine, I had almost 500k on my 280C before I traded it in. Good luck!
Brian

thanks for the info, I have heard the 280 is an excellent engine and I was lucky to find this in a euro model 280ce with low miles. thanks again.