
Chapter A: General Diagnosis
15
HC
CO
CO2
O2
NOx
Ignition Misfire
Compression
Loss
Rich Mixture
Lean Mixture
Minimal Timing
Retard
Excessive
Timing Retard
Advanced
Timing
EGR Operating
EGR Leaking
AIR Operating
Converter
Operational
Exhaust Leak
Worn Engine
Worn Camshaft
Lobes
Large
Increase
Some
Decrease
Some
Decrease
Some to Large
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Decrease
Some
Increase
Some
Decrease
Some
Decrease
Some to Large
Increase
Some to Large
Increase
Large
Increase
Some
Decrease
Some
Increase
Large
Decrease
Some
Increase
Large
Increase
Possible
Increase
No
Change
No
Change
Possible
Decrease
Some
Increase
Some
Increase
No
Change
No
Change
Some to Large
Decrease
Large
Decrease
Large
Decrease
Some
Decrease
Large
Increase
No
Change
No
Change
Small
Decrease
Possible
No
Change
No
Change
No
Change
Large
Decrease
Some
Increase
No
Change
No
Change
Possible
Increase
No
Change
Large
Decrease
Large
Decrease
Large
Decrease
Large
Increase
Possible
Increase
Some
Increase
Large
Decrease
Some
Increase
No
Change
Some
Increase
Some
Increase
Large
Decrease
Possible
Decrease
Some
Decrease
Possible
Decrease
Condition
Fig. 1-16.
Effect of engine condition on the formation of exhaust gasses.
• Rich fuel mixture
• Incorrect idle speed
• Excessive fuel pressure
• Leaking fuel injectors
Both HC and CO levels reading high at the same time
may be caused by the following conditions:
• Defective positive crankcase ventilation system
• Defective catalytic converter
• Defective manifold heat control valve
• Defective air pump
• Defective thermostatic air cleaner
Summary of Contents for ASE-A8
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