Exhaust System BACKPRESSURE

The exhaust system can be checked with a vacuum gauge or pressure gauge. Remove O2 sensor or air injection check valve, if equipped. Connect a 1-10 psi gauge and run engine at 2500 RPM. If exhaust system backpressure is more than 1 3/4-2 psi, exhaust system or catalytic converter is plugged.

If a vacuum gauge is used, connect it to manifold vacuum. Observe vacuum gauge. With engine running, partially open and hold throttle. If vacuum gauge slowly drops after stabilizing, exhaust system should be checked for restriction.