I have a 1993 Accord Station Wagon with about 160,000 miles. I have recently had a tune-up done. The engine vibrates at idle, especially when the a/c compressor comes on. The engine runs fine in normal driving. What is possible problem and correction? I've read elsewhere that there might be motor mount issues.

Yeah, that would be my first guess. Do a search and check it out, its a very common problem on 90-93 accords. Also, if thats the case, get it fixed, as when one gets worn out, the other will follow. It happened on my 90 Accord Sedan.