92 Subaru Legacy

About 15 seconds after I turn my key on, before I start the car, the fans start running full speed and the injectors start squirting and the coil starts firing. If I start the car before this happens the car runs fine, once the extra gas is burned off. It runs rich but seems to run very smoothly. My mechanic switched out the computer but the same thing happened and they can’t figure out what is wrong.