Pinpoint Test A: Restricted Exhaust System Test

WARNING: This page is about a different car, the 2004 Mercury Monterey and 2004 Ford Freestar. 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?
Yes

GO to A2

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 JACKING & 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)?
Yes

GO to A3

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)?
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.

No

The restriction is in the muffler assembly. INSTALL a new muffler. CLEAR the DTCs. TEST the system for normal operation.