Exhaust System Backpressure
- Exhaust system can be checked with vacuum gauge or pressure gauge. Remove O2 sensor or air injection check valve, if equipped. Connect a 1-10 psi gauge to port.
- Backpressure should be 1 1/4 psi (8.6 kPa) at idle. Increase engine speed to 2000 RPM. Reading on gauge should be 3 psi (20.7 kPa). If backpressure is higher at either RPM, exhaust system or catalytic converter is plugged.
- If a vacuum gauge is used, connect it to intake manifold vacuum. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge slowly drops after stabilizing, exhaust system should be checked for restriction.