Changing spark plugs on a Jaguar 448PN petrol engine is straightforward if you follow the correct steps. Start by letting the engine cool completely to avoid damage or injury. Remove the engine cover, then carefully disconnect the ignition coils one by one. Use a spark plug socket with an extension to remove old plugs. Before installing new ones, check the gap as per Jaguar specifications. Tighten gently to avoid thread damage. Reconnect coils, refit the cover, and start the engine to ensure smooth idle and improved performance.