Exhaust System Backpressure

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

Before replacing any components, check exhaust system for restrictions. The exhaust system has very low back pressure under normal conditions. For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and diagnosis should begin there. Use a vacuum gauge or a low-pressure (0-5 psi) gauge to check exhaust system.

If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Partially open throttle and hold steady. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for a restriction. If using a low pressure gauge, connect gauge in one of the following manners:

Check At AIR Check Valve

Remove AIR check valve. Install backpressure tester in place of AIR check valve.

Check At Oxygen Sensor

Remove heated oxygen sensor in front of catalytic converter, then at post-catalyst heated oxygen sensor. Install backpressure tester in place of HO2S. Test as specified. After test is completed, coat oxygen sensor threads with anti-seize compound before installation.

Removing the AIR check valve or HO2S sensor may set a DTC. When finishing this diagnostic procedure, ensure to clear all codes.