Symptom: Jetta GTX (engine model: AHP) engine idling shaking
    Troubleshooting: start the engine, the idle operation of the engine jitter, there are individual tank bad work, increase the throttle jitter slightly better, check the steps are as follows:
    1. First check the ignition system. Unplug the cylinder high voltage line plug in the spare spark plug, high voltage line and ignition coil connection, turn the ignition switch to start the engine operation, observe the cylinder spark are blue fire, spark is very strong. Remove the spark plug from the engine, the spark plug gap is normal, the electrode part of the combustion is good, brown, porcelain insulation is good. Fitted with spark plugs, high voltage lines, start the engine after the fire test, the cylinder are working, indicating that the ignition system is working properly.
    2. Check the fuel supply system. If the fuel supply is insufficient, it will cause the engine to shake. In the fuel distribution pipe and pressure oil inlet rubber pipe connection disconnect, string into the fuel pressure gauge, start the engine to check the fuel pressure, respectively, check the idling oil pressure, accelerate the change in oil pressure and turn off the pressure after the normal.
    3. Use the easy-pass decoder to check the engine electronic control system. Into the engine electronic control unit, query fault memory, no fault code display. If a fault code appears, you should first remove the corresponding fault, and then check the next step.
    4. Use Easy Netcom to read the data blocks of the engine computer, through the data to observe the performance of the components. Into the 007 data block, the second area shows 0.15V, the secondary display value is the oxygen sensor voltage, the general normal display should be between 0.1V to 0.9V beating display. Suspected oxygen sensor blockage, this value is the exhaust system feedback to the computer signal, affecting fuel injection. Replacement of an oxygen sensor failure is still not excluded.
    5. Read the data block 002, the fourth display area, show 2.2g / so. Generally show 2.7g / s or so more normal, this value shows the air flow meter measured air flow. Is to control the fuel mixing ratio of the important parameters, replace the air flow meter, the fault has not yet ruled out.
    6. According to the data block reading and replacement of components analysis, oxygen sensor and air flow meter is not a problem, the data block shows the value is measured, the oxygen sensor voltage is low, indicating that the fuel mixture is thin, air flow value is low, Gas volume is small, if the small amount of air intake to the control of the computer, the amount of fuel injection control computer to make the fuel injection becomes smaller, fuel mixture dilution that the intake of large, it is likely that the intake air leakage, redundant The air does not go through the air flow meter and enters the cylinder to burn.
    7. Check the air intake system without leakage. Another air intake channel is the activated carbon vacuum system. Check that the system found that the activated carbon tank solenoid valve can not be closed. In general the activated carbon system does not work, the solenoid valve should be closed. Replace the activated carbon tank solenoid valve troubleshooting, idle smooth and normal.
    Activated carbon cans are used to collect the fuel tank fuel tank device, but also the fuel tank to the atmosphere of the channel. In order to prevent fuel vapor from contaminating air, the activated carbon from the activated carbon tank collects and adsorbs the fuel vapor from the fuel tank to the engine combustion. Activated charcoal tank to the engine has a pipeline, the pipeline to install a solenoid valve, controlled by the engine computer opening and closing. When the engine speed and speed is high, the activated carbon solenoid valve open, through the inlet vacuum will be collected by the activated carbon fuel vapor into the inlet and then burn. When the activated carbon tank solenoid valve damage, normally open solenoid valve open and closed from the engine computer control, there is an air directly through the activated carbon tank and pipe into the intake pipe, and not through the air flow meter measurement, the engine computer to receive a more than normal Air volume of small air flow signal, so that the amount of fuel injection reduced, mixed gas dilute, resulting in insufficient engine power, engine jitter.