Service manual

G424F(FE) Service Manual 248 Chapter 8. Basic Troubleshooting
Chart T-1 Restricted Exhaust System
Check
Proper diagnosis for a restricted exhaust system is
essential before replacement of any components.
The following procedures may be used for diagnosis,
depending upon engine or tool used.
Check Atpre - Catalystoxygen (O2) Sensor
1. Carefully remove pre-catalyst oxygen (O2) sensor.
2. Install exhaust backpressure tester or equivalent
in place of O2 sensor using Snap-On P/N
EEVPV311A kit and YA8661 adapter or Mac tool
(see illustration).
3. After completing test described below, be sure to
coat threads of O2 sensor with anti-seize
compound prior to re-installation.
Illustration Notes
1. Backpressure gage
2. Pre-catalyst Oxygen (O2) sensor
3. Exhaust manifold
Diagnosis:
1. With the engine idling at normal operating
temperature, observe the exhaust system
backpressure reading on the gage. Reading
should not exceed 1.25 psig (8.61 kPa).
2. Increase engine speed to 2000 rpm and observe
gage. Reading should not exceed 3 psig (20.68
kPa).
3. If the backpressure at either speed exceeds
specification, a restricted exhaust system is
indicated.
4. Inspect the entire exhaust system for a collapsed
pipe, heat distress, or possible internal damage,
split welds, or cracked pipe.
5. If there are no obvious reasons for the excessive
backpressure, the catalytic converter is restricted
and should be replaced using current
recommended procedures.