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.

For temperature related engine running problems, I would check the ECT sensor and its associated wiring first. A given temperature will produce a corresponding resistance through the sensor. Instructions and a chart are given in the 700/900 FAQ accessible via the "features" drop down menu above.

A temperature switch in the radiator will turn on the electric fan and , I believe, advance the timing when closed above a certain temperature (212 F?) However, advanced timing usually does not cause loss of power. Still you might disconnect this switch and drive to see if it goes away.

Finally, are you getting an ignition knock or ping under the conditions you describe? if so the ignition computer will retard the timing until the knock goes away. Retarded timing will certainly cause poor acceleration.

Cold start and die can usually be solved by correcting any vacuum leaks, cleaning the throttle body, and setting base idle and mixture. (and timing)

HTH bagle 87 745t

I have not noticed any pre-ignition knocking. To me, it does feel like it surges a bit. The throtle body has never been cleaned to the best of my knowledge. Will check these things out. Thanks for the input.