When your Lincoln catalytic converter begins to fail, you will face dropping fuel mileage, poor driving performance and the risk of failing an emissions test. Your catalytic converter will usually fail when another component in the fuel/emission system stops working, leading to a too-rich fuel mixture in the exhaust. When unburned fuel ends up in the catalytic converter's very hot core, the fuel will ignite and raise the temperature levels further. Over time, the catalytic converter will suffer heat stress. The too-rich fuel mixture can be caused by failing fuel injectors, oxygen and other sensors. If your Lincoln's combustion system suffers from repeated misfires, unburned fuel will be sent into the exhaust system. So check for misfiring spark plugs, ignition leads and distributor caps to trace the cause of the misfires. Diagnosing whether the catalytic converter can be tricky. First, check the onboard diagnostic codes for any clues. Tracking the temperature levels at the front and end of the catalytic converter might provide clues. Use a laser pyrometer, which measures very high temperatures to check the heat levels of the inlet and outlet. If the cat is working correctly, the inlet will be much hotter than the outlet. Sometimes the catalytic converter can become clogged with leaking oil and coolant from the combustion system, so check for blockage with a pressure tester. Once the diagnosis confirms that you need a new catalytic converter, purchase a quality unit from our site.