EM-14
ENGINE MECHANICAL —
Idle HC/CO Concentration Check Method
4.
RACE ENGINE AT 2,500 RPM FOR APPROX. 2
MINUTES
5.
I
NSERT HC/CO METER TESTING PROBE INTO
TAIL PIPE AT LEAST 40 cm (1.3 ft)
6.
MEASURE HC/CO CONCENTRATION AT IDLE
Wait at least one minute before measuring to allow the
concentration to stabilize.
Complete the measuring within three minutes.
If the HC/CO concentration does not conform to regula-
tions, see the table below for possible causes.
Troubleshooting
HC
CO
Problem
Cause
High
Normal
Rough idle
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 intake and exhaust valves
5.
Leaky cylinder
High
Low
Rough idle
1. Vacuum leak:
(Fluctuating HC reading)
• PCV hose
•
EGR valve
•
Intake manifold
•
Air intake chamber
•
Throttle body
•
ISC valve
•
Brake booster line
2.
Lean mixture causing misfire
High
High
Rough idle
1.
Restricted air filter
(Black smoke from exhaust)
2.
Faulty EFI system
•
Faulty pressure regulator
•
Clogged fuel return line
•
Defective water temp. sensor
•
Defective air temp. sensor
•
Faulty ECU
•
Faulty injector
•
Faulty cold start injector
•
Faulty throttle position sensor
•
Air flow meter
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