Exhaust System Backpressure

Check exhaust system using a vacuum or pressure gauge. Remove heated O2 sensor or air injection check valve (if equipped). Connect a 1-10 psi pressure gauge, and operate engine at 2500 RPM. If exhaust system backpressure is greater than 1 3/4 - 2 psi, exhaust system or catalytic converter is plugged.

If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum slowly drops after stabilizing, check exhaust system for restriction.