Mazda 626 Station Wagon, Workshop Manual

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TROUBLESHOOTING
STEP INSPECTION RESULTS ACTION
2 Remove thermostat and inspect operation.
(See Section E)
Is thermostat okay?
Yes Engine coolant temperature and thermostat are
okay.
Go to next step.
No Access ECT V PID on NGS tester.
Inspect for both ECT V and temperature gauge
on instrument cluster readings.
If temperature gauge on instrument cluster
indicates normal range but ECT V is not same
as temperature gauge reading, inspect ECT
sensor.
If temperature gauge on instrument cluster
indicates cold range but ECT V is normal,
inspect temperature gauge and heat gauge unit.
3 Is throttle body free of contamination? Yes Inspect for air leakage from intake-air system
components while racing engine to higher
speed.
No Clean or replace throttle body.
4 Verify test results. If okay, return to diagnostic index to service any additional symptoms.
N0.7 ENGINE RUNS ROUGH/ROLLING IDLE
7 Engine runs rough/rolling Idle
DESCRIPTION
• Engine speed fluctuates between specified idle speed and lower speed and engine shakes
excessively.
• Idle speed is too slow and engine shakes excessively.
POSSIBLE
CAUSE
• Air leakage from intake-air system parts
• A/C system operation is improper.
• Spark leakage from high-tension leads
• Purge solenoid valve malfunction
• Improper operation of IAC valve
• EGR valve malfunction
• Erratic or no signal from CMP sensor
• Low engine compression
• Erratic signal from CKP sensor
• Poor fuel quality
• PCV valve malfunction
• Air cleaner restriction
• Restriction in exhaust system
• Disconnected electrical connectors
• Inadequate fuel pressure
• Fuel pump body mechanical malfunction
• Fuel leakage from fuel injector
• Fuel injector clogging
• Engine overheating
• Vacuum leakage
• Pressure regulator control (PRC) system malfunction
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 leakage 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”. (See
Section F)
Caution
• Disconnecting/connecting the quick release connector without cleaning it may possibly
cause damage to the fuel pipe and quick release connector. Always clean the quick
release connector joint area before disconnecting/connecting, and make sure that it is
free of foreign material.
F1-117