MX-5 Miata L4-1.8L DOHC (1996)
Idle/Throttle Speed Control Unit: Testing and Inspection
Idle Air Control Valve
BAC VALVE
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Connect the SST (System Selector) to the data link connector.
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Set switch A to position 1.
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Set the test switch to SELF TEST.
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Connect the SSTs (NGS) to the data link connector-2.
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Select the PID/DATA MONITOR AND RECORD function.
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Verify that the engine is cold condition, and start the engine.
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Select the "RPM" on the NGS display.
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Verify that the engine speed decreases as the engine warms up.
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Disconnect the SST (System Selector).
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If the engine speed will not decrease or decreases slowly, check the water hose connected to BAC valve for leakage and clogs.
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If the water hose is OK, inspect the following.
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Air valve
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IAC valve
IDLE AIR CONTROL VALVE
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Start the engine and run it at idle.
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Disconnect the IAC valve connector and verify that the engine speed changes.
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If the engine condition will not change, do as follows.
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Connect the SSTs (NGS) to the data link connector-2.
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Verify that diagnostic trouble code No. P0505 is not displayed. If code No. P0505 is shown, carry out troubleshooting of the code No. P0505.
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Select the SIMULATION TEST function on the NGS display.
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Change the duty value of the IAC valve to 100% by using the "IACV" and verify that the idle speed increases.
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If the idle speed increases, replace the ECM.
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If the idle speed does not change. Replace the IAC valve.
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Warm up the engine to normal operating temperature and run it at idle.
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Turn the electrical loads ON and verify that the engine speed is with in the specification.