Engine Performance problem
1995 Jeep Cherokee 4 cyl Four Wheel Drive Automatic
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We can be driving fast or slow, for a short distance or more than a day, when out of nowhere, the tack drops to zero. Some times it will start right back up, but usually it takes anywhere from 5 minutes to an hour before it will just as inexplicably start back up. While attempting to restart the car, the engine will try to turn over, it just won't catch.

The battery is fine, we've changed the gas filter, the air filter is clean, and we've replaced the spark plugs. Some have suggested that it seems electrical because it's so sudden. Others have said the gas pump is going or that maybe the catalytic converter is bad.

Ideas?