On the highway in rainy conditions my Grand Prix died when my brakes were applied.
A car in need of a simple tuneup may stall under those conditions. Check your spark plugs, ignition wires, and make sure you don't have any vacuum leaks. Stepping on the brakes drops the available vacuum and can trigger stallout conditions if you already have low vacuum. Last but not least, a clogged air filter can reduce intake air and fuel levels to stallout levels.
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