Pontiac Fiero 1988 Service Manual page 516

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI) 6E2-B-7
CHART B-1
RESTRICTED EXHAUST SYSTEM CHECK
ALL ENGINES
Proper diagnosis for a restricted exhaust system is essential before any components are replaced. Either of
the following procedures may be used for diagnosis, depending upon engine or tool used:
CHECK AT A. I. R. PIPE: OR CHECK AT O2 SENSOR:
1. Remove the rubber hose at the exhaust 1
manifold A.I.R. pipe check valve. Remove 2
check valve.
2. Connect a fuel pump pressure gauge to a hose
and nipple from a Propane Enrichment 3
Device (J26911) (see illustration).
3. Insert the nipple into the exhaust manifold
A.I.R. pipe.
DIAGNOSIS:
1. With the engine idling at normal operating temperature, observe the exhaust system backpressure
reading on the gauge. Reading should not exceed 1 j psi (8.6 kPa).
2. Accelerate engine to 2000 rpm and observe gauge. Reading should not exceed 3 psi (20.7 kPa).
3. If the backpressure, at either rpm, exceeds specification, a restricted exhaust system is indicated.
4. Inspect the entire exhaust system for a collapsed pipe, heat distress, or possible internal muffler failure.
5. If there are no obvious reasons for the excessive backpressure, a restricted catalytic converter should be
suspected and replaced using current recommended procedures.
Carefully remove O2 sensor.
Install Borroughs Exhaust Backpressure
Tester (BT 8515 or BT 8603) or equivalent in
place of O2 sensor (see illustration).
After completing test described below, be
sure to coat threads of O2 sensor with anti-
seize compound P/N 5613695 or equivalent
prior to re-installation.
4-24-86
7 S 3 3 4 0 - 6 E