6. Unstable idle speed at any time Table 1-56 74 S/N Operation Test Results Actions 1 Turn the ignition switch to ON. Check if there is trouble information records with a diagnostic instrument. Yes Remove the trouble No Next step 2 Check if the idle speed actuator or the stepper motor idle speed actuator is locked. Yes Replace idle speed actuator No Next step 3 Turn the ignition switch to ON. Connect an adapter between the ECU and the harness. Check the voltage of the pin J1-27, J1-43 (signal output end of the intake air temperature sensor and coolant temperature sensor), J1-54, J1-33, J1-53, J1-34 (signal output end of the stepper motor), J1-54, and J1-53 of the ECU. Is the voltage normal?
Yes Check harness and interface No Next step 4 Run the engine at an idle speed. Cut off each cylinder in sequence. Check if the rotation speed of the engine is dcreased or fluctuated. Yes 8 No Next step 5 Check the fuel injector of each cylinder for normal operation. Yes Next step No Check fuel injector and harness 6 Check the resistance of the high voltage wire for each cylinder. Is the resistance OK? Yes Next step No Replace 7 Check the ignition coil for damage or crack. Yes Replace No Next step 8 Check the spark plug for normal operation. Yes Next step No Replace spark plug 9 Connect the fuel pressure gauge valve.
Short-circuit the pin J1-47 and the pin J1-73 of the fuel bump relay, and run the fuel pump. Check if the fuel pressure is about 380kPa. Yes Next step No 13 10 Connect the battery and the fuel injector with a special connector. With the voltage supply of 12V, check the fuel injector for normal operation. Yes 12 No Next step 11 Clean the fuel injector and check the fuel injector for normal operation. Yes Next step No Replace fuel injector