<strong>Manifold Absolute Pressure (MAP)</strong><br />Unlike what you might find at your local hiking shop, this MAP provides input to a computer that isn't made by Garmin or Magellan. Located on the firewall behind and above the engine or on the throttle body, the MAP sensor provides the computer with the amount of pressure the atmosphere exerts on the Jeep. Why do you care? Have you ever driven a carbureted Jeep at elevation without changing the jets? At higher elevations, there is less combustible air per cubic yard than at sea level. What that means to a carbureted Jeep is that the mechanically set mixture at sea level for this much air with that much fuel isn't enough anymore, and the amounts need to be doubled or tripled for the engine to run well. In a carbureted rig, this means at higher elevations, the Jeep becomes gutless, and almost not worth driving. The MAP sensor acts like a jet change without any of the nasty seal mess, fuel spills, or setting of float levels. As the elevation changes, and air pressure varies, this sensor tells the computer to increase or decrease the amount of fuel to the engine through the amount of time each injector opens. While it isn't perfect, it does a good job of compensating for a lack of combustible air at higher elevation.