Pinpoint Test A: Restricted Exhaust System Test

WARNING: This page is about a different car, the 2004 Lincoln LS. However, it is still accessible from the selected car via links, so may be relevant.

A1 EXHAUST SYSTEM INSPECTION
- Inspect the exhaust system for damage or deterioration. Look for cracks, punctures, leaks, loose connections, dents or unusual bending.
- Is the exhaust system OK?
  1. Yes : GO to A2.
  2. No : REPAIR or INSTALL any damaged or deteriorated exhaust components. Test the system for normal operation.
A2 BACK PRESSURE TEST
- Position vehicle on a hoist. Refer to LIFTING .
- Connect a tachometer.
- Using the special tool, remove the upstream heated oxygen sensor (HO2S).
- Install the back pressure gauge.
- Start the engine and gradually increase the engine speed to 2,000 RPM with the transmission in NEUTRAL.
- Is the back pressure greater than 27.6 kPa (4 psi)?
  1. Yes : GO to A3.
  2. No : No indications of a restriction have been detected. CONDUCT a diagnosis on other suspect systems. CLEAR the DTCs.
A3 BACK PRESSURE TEST - CATALYTIC CONVERTER(S) ON, MUFFLER(S) OFF
- Turn the engine OFF.
- Disconnect the muffler assembly from the catalytic converter.
- Repeat the back pressure test.
- Is the back pressure greater than 27 kPa (4 psi)?
  1. Yes : The restriction is in the catalytic converter. INSTALL a new catalytic converter. INSPECT the muffler to be sure the catalytic converter debris has not entered the muffler. CLEAR the DTCs. TEST the system for normal operation.
  2. No : The restriction is in the muffler assembly. INSTALL a new muffler. CLEAR the DTCs. TEST the system for normal operation.