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2008 - MX-5 - Engine

NO.7 SLOW RETURN TO IDLE [LF]



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


Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION

1

Connect the M-MDS to the DLC-2.

Turn the ignition switch to the ON position (Engine off).

Retrieve any DTCs.

Are there any DTCs displayed?

Yes

DTC is displayed:

Go to the appropriate DTC inspection.

(See DTC TABLE [LF].)

No

No DTC is displayed:

Go to the next step.

2

Remove thermostat and inspect operation.

Is thermostat normal?

Yes

ECT and thermostat are normal.

Go to the next step.

No

Access ECT PID on the M-MDS.

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 contamination?

Yes

Inspect for air leakage from the intake-air system components while racing the engine to higher speed.

No

Clean or replace throttle body.

4

  • Verify test results.

    • If normal, return to diagnostic index to service any additional symptoms.

      (See SYMPTOM DIAGNOSTIC INDEX [LF].)

    • If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.

      • If vehicle is repaired, troubleshooting completed.

      • If vehicle is not repaired or additional diagnostic information is not available, replace the PCM.

        (See PCM REMOVAL/INSTALLATION [LF].)




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