Troubleshooting
If the CO/HC concentration does not comply with
regulations, perform troubleshooting in the order
given below.
(a) Check heated oxygen sensor operation.
(See MFI System on page EG2–252)
(b) See the table below for possible causes, and then
inspect and correct the applicable causes if neces–
sary.
1. Restricted air filter
2. Plugged PCV valve
3. PAIR system problems
4. Faulty M F I systems:
• Faulty pressure regulator
• Clogged fuel return line
• Defective ECT sensor
• Defective intake air temperature sensor
• Faulty ECM
• Faulty injector
• Faulty cold start injector
• Faulty throttle position sensor
• Faulty volume air flow meter
1. Faulty ignitions:
• Incorrect timing
• Fouled, shorted or improperly gapped plugs
• Open or crossed high–tension cords
• Cracked distributor cap
2. Incorrect valve clearance
3. Leaky EGR valve
4. Leaky intake and exhaust valves
5. Leaky cylinder
1. Vacuum leaks:
• PCV hose
• EGR valve
• Intake manifold
• Air intake chamber
• Throttle body
• Brake booster line
2. Lean mixture causing misfire
Rough idle
(Black smoke from exhaust)
Rough idle
(Fluctuating HC reading)
Rough idle
Problems
Causes
Normal
High
High
High
High
Low
–ENGINE ENGINE MECHANICAL
EG2–29
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