Q: What would cause acceleration without stepping on the gas while stopped?

It would be hard to pinpoint the exact cause. A couple of possibilities could be a vacuum leak. If the engine is sucking in too much air, it could raise the engine speed, possibly drastically if a ;large vacuum leak suddenly occurred, such as the brake vacuum booster line breaking or coming loose. Another possibility could be in the throttle control. Most of today’s engines, do not have a mechanical connection (throttle cable) between the gas pedal and the engine. This is done with potentiometers, sensors, and switches. Think dimmer switch on a ceiling light. Sensors on the gas pedal, tell the engine control unit exactly how far you’ve pushed the gas pedal. This then sends a signal to the stepper motor on the throttle body, which open the throttle in the same amount as you have pushed the gas pedal. A short or defect in any part of this system could have caused your situation.

Have it towed to the nearest Jeep service department as soon as possible for further inspection. You may want to contact Jeep Customer Service and notify them of what occurred.