I have a 1991 Volvo 740 which has a persistent problem to which no one has found a solution.

The car runs well in general, and is well taken care of, but it often fails to start. Usually it gets a bit harder to start and just degrades over a matter of days or weeks to the point where it won't anymore. The engine turns over, but doesn't actually start.

We've taken this to a good Volvo mechanic quite a number of times. Often, when the car is towed into the garage, the problem isn't there anymore. It's very frustrating because it's a bit like that old Warner Brothers cartoon about the singing mouse who won't sing when anyone other than his owner is watching.

This problem is severe enough that we're on the verge of ridding ourselves of the car. We don't want to; other than this, it's been a good car. It has about 265,000 miles on it, and we'd like to get at least a few more years of service out of it. But, obviously, we can't abide a starting problem.

If anyone has suggestions about what this might be, particularly some strange alley that an otherwise competent and experienced Volvo mechanic might have missed, I'd be very interested to hear them. We really don't want to sell this car unless we must.