Exhaust System Backpressure

Measure exhaust system backpressure with a vacuum or pressure gauge. Remove O2 sensor. Connect 0-10 psi pressure gauge in place of sensor. Run engine at 2500 RPM. If exhaust system backpressure is greater than 2 psi (0.14 kg/cm² ), exhaust system or catalytic converter is plugged. If using vacuum gauge, connect it to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum drops slowly after stabilizing, inspect exhaust system for restrictions.