2005 Chrysler PT Cruiser Owner's Manual - Page 274

274 MAINTAINING YOUR VEHICLE 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 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 Engine data Label located under the hood for the proper type of spark plug for use in your vehicle. Ignition Wiring System The ignition cables should be kept clean and properly connected. Terminals should be fully seated. Cracked, damaged, or faulty cables should be replaced. Catalytic Converter The catalytic converter requires the use of unleaded fuel only. Leaded gasoline will destroy the effectiveness of the catalyst 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.