TROUBLESHOOTING
If the HC/CO concentration does not comply with
regulations, perform troubleshooting in the order
given below.
1. Check oxygen sensor operation
(See page EG1–212)
2. See the table below for possible cause, and then
inspect and correct the applicable causes if neces–
sary.
1. Clogged air filter
2. Plugged PCV valve
3. Pulsed Secondary Air Injection (PAIR)
system problems
4. Faulty MFI system:
• Faulty pressure regulator
• Clogged fuel return line
• Faulty volume air flow meter
• Defective engine coolant temp. sensor
• Defective intake air temp. sensor
• Faulty ECM
• Faulty injector
• Faulty cold start injector
1. Faulty ignition:
• 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 exhaust valves
5. Leaky cylinder
1. Vacuum leak:
• Vacuum hose
• Intake manifold
• Intake chamber
• PCV line
• Throttle body
Rough idle
(Black smoke from exhaust)
Rough idle
(Fluctuating HC reading)
Rough idle
Symptoms
Normal
Causes
High
High
High
High
Low
–ENGINE ENGINE MECHANICAL
EG1–13
To Next Page
Loading...
