Mazda MX-6 1998, Workshop Manual

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TROUBLESHOOTING [ENGINE CONTROL KL]
13 POOR FUEL ECONOMY
DESCRIPTION Fuel economy unsatisfactory
POSSIBLE
CAUSE
• Contaminated air cleaner element
• Improper transmission fluid level
• Poor fuel quality
• Improper coolant level
• Spark plug malfunction
• Brake dragging
• Contaminated mass airflow sensor
• Exhaust system clogged
• Engine cooling system malfunction
• W eak spark
• Erratic or no signal from camshaft position sensor
• Inadequate fuel pressure
• PCV valve malfunction
• Improper valve timing due to timing belt skip out
• Improper engine compression
Warning
Following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read
following warnings before performing fuel system service:
• Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep
sparks and flames away from fuel.
• Fuel line spills and leaks are dangerous. Fuel can ignite and cause serious injuries or death
and damage. Fuel can also irritate skin and eyes. To prevent this, always complete “BEFORE
REPAIR PROCEDURE” and "AFTER REPAIR PROCEDURE” described in this manual.
cr 0 1 -1 4 BEFORE REPAIR PROCEDURE
cr 0 1 -1 4 AFTER REPAIR PROCEDURE
STEP INSPECTION ACTION
1 Check following:
• Contaminated air cleaner element.
• Transmission fluid level.
• Fuel quality.
• Coolant level.
Are all items okay?
Yes Go to next step.
No
Service as necessary.
Repeat step 1.
2
Retrieve and record any continuous memory,
KOEO and KOER DTCs.
Are there any DTCs displayed?
Yes
Go to appropriate DTC test.
No Go to next step.
3 Connect NGS tester to DLC.
Access ECT PID.
Drive vehicle while monitoring PID.
• ECT PID
tr 0 1 -40B ENGINE COOLANT
TEMPERATURE SENSOR
INSPECTION [KL]
Is PID within specification?
Yes Go to next step.
No
Check for coolant leak, cooling fan and condenser fan
operations or thermostat operation.
4 Is strong blue spark visible at each
disconnected high-tension lead while cranking
engine? Yes Check follows:
• Spark plug(s) malfunction.
• CMP sensor improperly installed.
• Trigger wheel damage on camshaft.
• Open or short circuit on CMP sensor.
• Open or short circuit between CMP sensor and PCM.
Repair or replace malfunctioning part.
If okay, go to next step.
No Check follows:
• High-tension leads.
• Ignition coil and connector.
0 1 -0 1 B -1 55