I have kept my 2004 SAAB 9.3 ARC convertible running for 173K, and have hoped for a few more. The 9.3 recently has developed a sudden strong engine vibration. You can feel it in the steering wheel, and the whole car shakes. In park, drive, reverse...vibration in all. Least annoying at about 60 MPH on highway. No power loss, no overheating, Engine light not on...no codes come up. My thoughts went to vacuum hose, exhaust leak, engine mount...my SAAB mechanic came up empty. If it is internal...bearing , timing chain issue, it would be fatal, but hoping it is a simpler overlooked fix...