2004 Jeep Grand Cherokee Owner's Manual - Page 261

MAINTAINING YOUR VEHICLE 261 Drive Belts - Check Condition and Tension At the mileages shown in the appropriate "Maintenance Schedule," check all drive belts for condition and proper tension. Improper belt tension can cause belt slippage and failure. Inspect the drive belt for evidence of cuts, cracks, or glazing and replace them if there is any sign of damage which could result in belt failure. If adjustment is required, adjust the belts according to the specifications and procedures shown in the Service Manual. Special tools are required to properly measure tension and to restore belt tension to factory specifications. Also, check belt routing to make sure there is no interference between the belts and other engine components. Spark Plugs Spark plugs must fire properly to assure engine performance and emission control. New spark plugs should be installed at the specified mileage. The entire set should be replaced if there is any malfunction due to a faulty spark plug. Refer to the "Vehicle Emission Control Information" label in the engine compartment for spark plug information. Catalytic Converter The catalytic converter requires the use of unleaded fuel only. Leaded gasoline will destroy the effectiveness of the converter as an emission control device. Under normal operating conditions, the catalytic converter will not require maintenance. However, it is important to keep the engine properly tuned to assure proper catalyst operation and prevent possible catalyst damage. 7