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12.11 Periodic Unsteadiness (Have to Perform Self-study again after ECU is Power off)
Yes Remove the failure displayed 1 Put the ignition switch to “ON”. Use a failure diagnostic tester to check if any failure information record exists. No Next step Yes Next step 2 Check the air cleaner and look if it is open.
No Replace Yes Next step 3 After starting successfully, check if air intake consumption of the engine at idle speed is around 300Kg/h (remember to check if cylinder pressure is normal). No Check and repair air intake and leak Yes 7 4 Let engine run at idle speed, spark out cylinder in turn, and observe if engine revolution will fall and fluctuate (it is prohibited to carry out spark out experiment by disconnecting ignition cable). No Next step Yes Next step 5 Turn on ignition switch, connect an adaptor between ECU and harness, and then check if the voltage between 17# and 42# pins of ECU, between 39# and 17# pins of ECU (signal output terminal of intake air temperature sensor and coolant temperature sensor) as well as 64#, 65#, 66#, 67# pins of ECU (for control of DC motor) is normal. No Repair or replace cable Yes Next step 6 Let engine run at idle speed, after coolant temperature reaches normal value, then use a diagnostic tester to check if ignition advance angle of the system is normal. No Check other part Yes Sweep 7 Check air intake system for such failures that may affect working of engine as blocking and air leak etc. No Next step Yes Replace fuel 8 Check if fuel is deteroprated or moisture.
No Next step Yes Next step 9 Use a special joint to directly provide a 12V power supply and intermittent ground wire from battery to injector and check if the injector can work intermittently. No Check and repair oil injector and related wires Yes Next step 10 Check if the resistance values of cylinders’ ignition cable are normal.
No Replace Yes Replace 11 Check if the ignition coil is damaged or cracked.
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