Mazda 6 2002 - No.7 Slow Return to Idle

F198
TROUBLESHOOTING
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NO.7 SLOW RETURN TO IDLE
A6E398018881W09
Diagnostic procedure
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26 Is air leakage felt or heard at intake-air system
components while racing engine to higher
speed?
Yes Repair or replace.
No Go to next step.
27 Inspect engine condition while tapping EGR
valve housing.
Is engine condition improved?
Yes Replace EGR valve.
No Go to next step.
28 Note
• The following test should be performed for
vehicles with variable valve timing control
system. Go to next step for vehicles
without variable valve timing control
system.
Inspect variable valve timing control system
operation.
(See F239 Variable Valve Timing Control
System Operation Inspection.)
Does variable valve timing control work
properly?
Yes Go to next step.
No Repair or replace malfunctioning parts.
29 Is engine compression correct? Yes Inspect valve timing.
No Inspect for causes.
30 Verify test results.
• If okay, return to diagnostic index to service any additional symptoms.
• If malfunction remains, replace PCM.
STEP INSPECTION RESULTS ACTION
7 SLOW RETURN TO IDLE
DESCRIPTION Engine takes more time than normal to return to idle speed.
POSSIBLE CAUSE
• ECT sensor malfunction
• Thermostat is stuck open.
• Throttle body malfunction
• Air leakage from intake-air system
STEP INSPECTION RESULTS ACTION
1 Connect WDS or equivalent to DLC-2.
Retrieve any continuous memory, KOEO and
KOER DTCs.
Are there DTCs displayed?
Yes DTC is displayed:
Go to appropriate DTC test.
No No DTC is displayed:
Go to next step.
2 Remove thermostat and inspect operation.
(See E7 THERMOSTAT REMOVAL/
INSTALLATION.)
(See E8 THERMOSTAT INSPECTION.)
Is thermostat okay?
Yes ECT and thermostat are okay.
Go to next step.
No Access ECT PID on WDS or equivalent.
Inspect for both ECT PID and temperature gauge on
instrument cluster readings.
If temperature gauge on instrument cluster indicates
normal range but ECT PID is not same as temperature
gauge reading, inspect ECT sensor.
If temperature gauge on instrument cluster indicates
cold range but ECT PID is normal, inspect temperature
gauge and heat gauge unit.
3 Is throttle body free of contaminations? 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.
• If malfunction remains, replace PCM.