I have a Volvo 740 Turbo wagon. For the last year or more it appears that, when the under-hood temperature rises, the accelleration becomes very sluggish. The turbo gauge goes into boost but the vehicle is very slow to accellerate. It also feels like there is some surging. When the ambient temperature is in the 80's or above, this problem shows up sooner than when the outside temperature is cooler.

The mileage is approximately 120,000. The vehicle has been well maintined and was tuned up by the Volvo dealer less than 5,000 miles ago. They feel that it might be a turbo or throtle body problem but have not run any diagnostics on it. I also notice that when our Florida temperatures are very warm, when I first start up in the morning, it will die when I put it into gear. Once I re-start it, it runs fine. This might be unrelated but also seems to be related to the outside temperature.