The MAP sensor in your 1998 Jeep Cherokee is responsible for measuring the airflow going to the engine. MAP stands for "manifold absolute pressure". As the name suggests, the MAP sensor is mounted on the intake manifold. When the sensor malfunctions, you'll notice rough idling and general poor performance. When the sensor fails, the Jeep will regularly stall out -- even when you're driving at a constant speed. This is because the engine's computer is trying to "guess" the correct air-to-fuel ratio without a properly working sensor.
Disconnect the battery. Loosen the retaining nut on the negative cable clamp and slide the clamp off the negative battery terminal.
Locate the MAP sensor on the intake manifold on the back of the engine.
Unplug the electrical connector running to the manifold.
Locate the two screws on the MAP sensor that hold the sensor to the manifold. Remove the two screws that hold the sensor in place and pull the sensor off the manifold.
Insert the new sensor into the manifold and line up the mounting holes on the sensor with the mount on the manifold.
Thread and tighten the retaining screws.
Plug the electrical connector back into the sensor. Reconnect the battery.
