Exhaust System Backpressure
WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2002 Mercury Sable, 2002 Mercury Grand Marquis, 2002 Mercury Cougar, 2002 Lincoln Town Car, and 2002 Lincoln LS. However, it is still accessible from the selected car via links, so may be relevant.
The exhaust system can be checked with a vacuum or pressure gauge. If using a pressure gauge, remove oxygen sensor or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge and run engine at 2500 RPM. If exhaust system backpressure is greater than 2 psi, exhaust system or catalytic converter is plugged.
If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port. Start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, check exhaust system for restriction.