Jeep Grand Cherokee 2004: Problem occurs intermittently. Some days there are no problems. Other days it stalls out as the car first starts. Have to pump for a couple of minutes. Gear sticks on the 2nd. We have already changed the filter, cleaned the throttle, added treatments to the gas. We purchased a new fuel pump but have not installed it yet. When the jeep stalls the brakes fail. What should we try?