My wife's wagon runs rich when the engine is cold - bad enough to foul the plugs and make it run crappy if you drive it for several short trips in a row. Once the engine reaches operating temperature, it runs fine. If you don't drive short trips too much, the car runs fine also. It's only when you drive frequent short trips that the problem surfaces. Problem seems worse in cold weather.

This car has the 'Regina' fuel system, if that matters.

Fuel pressure regulator and temp sensor have been replaced. No help.

My mechanic thinks it's the computer and recommends replacing it ($).

Any other ideas?