EM
−
2
−
ENGINE MECHANICAL
CO/HC
505
Author:
Date:
1996 LAND CRUISER (RM451U)
6.
TROUBLESHOOTING
If the CO/HC concentration does not comply with regulations,
troubleshoot in the order given below.
See the table below for possible causes, and then inspect and
correct the applicable causes if necessary.
CO
HC
Problems
Causes
Normal
High
Rough idle
3. Faulty ignitions:
S
Incorrect timing
S
Fouled, shorted or improperly gapped plugs
S
Open or crossed high
−
tension cords
S
Cracked distributor cap
4. Incorrect valve clearance
5. Leaky EGR valve
6. Leaky intake and exhaust valves
7. Leaky cylinders
Low
High
Rough idle
(Fluctuating HC reading)
1. Vacuum leaks:
S
PCV hose
S
EGR valve
S
Intake manifold
S
Air intake chamber
S
Throttle body
S
IAC valve
S
Brake booster line
2. Lean mixture causing misfire
High
High
Rough idle
(Black smoke from exhaust)
1. Restricted air filter
2. Faulty SFI systems:
S
Faulty pressure regulator
S
Clogged fuel return line
S
Defective ECT sensor
S
Faulty ECM
S
Faulty injector
S
Faulty throttle position sensor
S
Faulty MAF meter
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