Volkswagen Santana GX sedan idling instability

       Mileage over 200,000 km of Shanghai Volkswagen Santana GX sedan. While the engine is able to start the car, but in idle condition is not running smoothly.
       Troubleshooting:
     (A) Failure Cause Analysis
       The reason there are many unstable engine idling, the air supply system blockage or leakage, poor fuel oil supply system, ignition system misfire or weak spark ignition timing is not correct, such as are likely to cause the engine to idle instability .
     (2) Troubleshooting Methods
       Check carburetor oil, in the normal range; check intake system, without clogging and leak case; check the ignition timing, compliance; checking high voltage fgtech galletto spark with high-pressure fire test methods and found that the spark was weak. Weak spark causes the various components and circuit comprises an ignition coil and the high voltage circuitry and low voltage circuits.
       Check the ignition coil resistance, the resistance of the resistance of the primary winding and a secondary winding were within the normal range, check the low pressure line connection without exception; replacement of the ignition coil failure remains. Therefore, the suspected cause of the malfunction outside the high-pressure circuit of the ignition coil. Check the central high-voltage and high-voltage resistance of the sub-cylinder found in many large than normal, indicating high voltage wires are aging.
     (3) failure treatment measures
       After the replacement of the high-voltage wires, idling unstable fault disappears, troubleshooting.
       Failure Analysis: Shanghai Santana GX sedan engine ignition system, the high-voltage wires are formed with a damping resistor for suppressing radio interference. High pressure damping resistor wire and fiber from a mixture of a carbon, a high pressure resistance of the wire after aging BMW ICOM increases, so that high voltage circuit is energized (arcing spark plug) ignition energy consumption increases accordingly, resulting in weakening the spark ignited rate decline, the light engine fuel consumption increases, idling unstable; severe, the engine can not start.
       Sometimes encounter resistance of high-voltage wires within the normal range, but due to high voltage wire insulation is damaged and cause leakage, but also may cause difficulty starting the engine, idle instability and other symptoms. Therefore, when high voltage wire maintenance, inspection of high voltage wires should not be overlooked or without breakage.
http://www.uobd2.net/wholesale/da-dongle-j2534-sdd-vci-device-for-jaguar-land-rover.html