My Infinity '93 sedan vibrates at idle and also at various speeds. There are no service message lights. Mechanic says there is spark and fuel at idle on all cylinders, except 2 cylinders have no compression. He suggested may be camshaft, but would be costly to even find that out. Any ideas?
Your mechanic’s theory sounds reasonable. I would think that a definitive diagnosis of low compression could be obtained for about $100 of shop time. It involves a compression and leak-down test where they check to see where the leaking air is going (intake/exhaust/or crankcase). If it is not leaking anywhere, then the problem is a cam.
The trouble is that most problems that cause low compression will cost more to fix than you would likely be willing to invest in a car of that age. If the car has over 200k miles, this may be the end of the road.
It can be difficult to drive a 16 year-old car unless you are a do-it-yourselfer. You are often faced with tough decisions on big investments without complete data on the extent of the problem.