Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.

NO.7 SLOW RETURN TO IDLE DIAGNOSTIC PROCEDURE

STEP	INSPECTION	RESULTS	ACTION
1	Connect the WDS or equivalent 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 applicable DTC inspection. (See DTC TABLE .)
1		No	No DTC is displayed: Go to the next step.
2	Remove the thermostat and inspect operation. (See THERMOSTAT REMOVAL/INSTALLATION .) (See THERMOSTAT INSPECTION .) Is the thermostat normal?	Yes	The ECT and the thermostat are normal. Go to the next step.
2		No	Access the ECT PID on the WDS or equivalent. Inspect the readings on both ECT PID and the temperature gauge on the instrument cluster. If the temperature gauge on the instrument cluster indicates the normal range but the ECT PID is not the same as the temperature gauge reading, inspect the ECT sensor. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION .) If the temperature gauge on the instrument cluster indicates the cold range but the ECT PID is normal, inspect the temperature gauge and the sending unit. (See WATER TEMPERATURE GAUGE .)
3	Is the throttle body free of contamination?	Yes	Go to the next step.
3	Is the throttle body free of contamination?	No	Clean or replace the throttle body.
4	Inspect for air leakage from the intake-air system components while racing the engine to a higher speed. Is there air leakage from intake-air system?	Yes	Repair or replace the malfunctioning parts according to the inspection results.
4		No	Inspect the eccentric shaft bypass valve. (See ECCENTRIC SHAFT BYPASS VALVE .)
5	Verify test results. If normal, return to the diagnostic index to service any additional symptoms. If the malfunction remains, inspect the related Service Bulletins and/or the On-line Repair Information and perform the repair or diagnosis.