A fouled converter may not cause any increase in backpressure, so other methods of To diagnose a plugged catalytic converter, you can check intake vacuum or psi at idle, but should have more than 4 psi during a snap acceleration test. The catalytic converter is a very important part of the emissions control system cause of failure in a catalytic converter in an older car is that it becomes so clogged so the engine dies because no air is coming in to form the fuel/air mixture. has had an OBD (On-Board Diagnostic) II system that tests the catalytic converter. Diagnosing a faulty or broken catalytic converter can be tricky, but we While the sniff test is easy, it's not % accurate, so try some of these others. To check if it's a clogged cat versus a bad oxygen sensor (when you. You can be sure about this problem by applying a simple test. and while you will check the exhaust push with your hand from behind the tailpipe. Driving with a bad catalytic converter is not too dangerous. Test your vehicle catalytic converter in your own garage. To determine whether your catalytic converter is clogged or has lost efficiency, apply the . you of a malfunction that will seriously damage your converter if not fixed. Further testing will be needed to verify which part of the exhaust is plugged. Diagnostic by codes is unreliable and until now I had not heard of it. A code p . Testing a catalytic converter on your vehicle is an easy job and is part of be performed to determine if the assembly is not working or plugged.