Toyota Land Cruiser 1988 Repair Manual page 40

HC
co
High Normal
High Low
High High
ENGINE MECHANICAL- Engine Tune-up EM-9
Problem
Rough idle
Rough idle
4. RACE ENGINE AT 2,500 RPM FOR APPROX. 2
MINUTES
5. INSERT HC/CO METER TESTING PROBE INTO
TAIL PIPE AT LEAST 40 em (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.
lfthe HC/CO concentration does not conform to regula-
tions, see the table blow for possible causes.
Troubleshooting
Cause
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
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
Rough idle
1.
Restrivted 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