George,

I would look at the spark plugs. If they have not been changed for more than 40,000 miles, one or more of them easily could be fowled.

Also, have you replaced the head gasket on this car yet? If not, it is probably leaking at the back of the head on the right side, and from the front of the head on the right side as well. Not that these external leaks would cause this problem, but at 97,000 miles, it is possible that the head gasket is leaking internally as well. Your dealer should, however, be familiar with this problem.