A mileage of about 110,000 km, with ATK engine FAW-Volkswagen Jetta Avant Garde GiX car. When the engine speed reaches 3000r/min performed shifting, engine is not running smoothly, the vehicle have punch feeling, high-speed driving weakness.
Fault Diagnosis: use VAG VAS 5054A diagnose the the engine electric control system, no fault code memory. Check the ignition coils, harness connector reliable connection. Remove the spark plug of each cylinder to sparkover experiment, sparks strong. Remove the fuel filter, found the filter is dirty, suspect the fuel quality of the fuel tank is poor or oil plug. So after removed the fuel tank, thoroughly clean fuel pump strainer and fuel tank, re-add high quality clean fuel, and replace the fuel filter, install fuel pressure gauge to measure the fuel system pressure, when engine idling the fuel pressure is 250kPa, when rapid acceleration is 300kPa. To keep the pressure at above 200kPa, the measured values were normal. Use the electrical barrier of multimeter to Measure the fuel injector resistance is 15Ω, meet the specified value.
Disconnect throttle position sensor harness connector, found that the plug connection is reliable, the pins in good contact, but have some dirt near the throttle. After cleaned, use VAS 5054A check engine speed when the throttle closed or open sensitive reaction and accurate. Check oxygen sensor voltage 0. 1 ~ 0. 8V changes, proved oxygen sensor is working properly. Check the crankshaft position sensor, after measuring, the signal output is normal, the harness connector in good condition. Performed parts replacement test, after replaced the control unit, intake air pressure sensor, throttle body and the ignition coils, the fault persists. Check each sensor element plug, found 2 knock sensor harness connector plug and socket looks something was amiss. After pluged two knock sensor plug back in place to test, the results returned to normal, the fault completely ruled out.
Later after understanding to know that the car had been replaced knock sensor. Since the model of two knock sensor plugs as easily reversed, although reversed but not affect the engine normal start, but after 2 connector reversed cause the control unit receives the wrong signal, causing the engine work abnormal.
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