Symptom: a 2001 annual production of modern Sonata 2.7 car, equipped with V6 engine, mileage of 260,000 km, the user reflects the car in the recent driving in the break, when the vehicle manned more trouble when the phenomenon is particularly evident.
    Troubleshooting: found in the engine running, you can hear the ignition coil at the abnormal "bang" sound, remove the engine cover, identified as the first cylinder high voltage line leakage. Remove the spark plug check, you can see the contacts have been ablated, so replace the high-voltage lines and spark plugs. Later, the test, found that the car has not made a break, but there has been another fault. The vehicle in the driving sometimes fault warning light will be lit, especially when the vehicle waiting for traffic lights when the shift lever from the D block into the N block, the engine failure light is definitely bright. After returning to the factory with the fault diagnosis instrument on the engine electronic control system for detection, found the following fault content: ① air flow meter signal value is too low. ② The first oxygen sensor 1 is disabled. ③ The first oxygen sensor 2 is disabled. ④ air-fuel ratio correction anomaly (B1). ⑤ air-fuel ratio correction anomaly (B2).
    According to these fault prompts, maintenance personnel to view the relevant data flow, found the following two data show abnormal: ① air flow meter signal voltage 0.35V. ② before and after the two oxygen sensor signal voltage is 0.3V. Air flow meter signal voltage is less than the standard value generally caused by the following reasons: ① air flow meter measurement error. ② There is a leak in the intake system, which is also consistent with the oxygen sensor data. Oxygen sensor signal voltage is low due to the following reasons: ① oxygen sensor damage. ② There is leakage in the intake system. ③ fuel injection is insufficient. In order to determine whether the oxygen sensor itself is the problem, we first do the oxygen sensor signal feedback test, when the throttle at the injection of some carburetor cleaning agent, the oxygen sensor signal voltage can be very sensitive to change, indicating that the oxygen sensor Itself is working properly, the cause of the fault should be that the engine does exist too thin mixture of the situation. For this maintenance personnel first clean the air flow meter, installed after the test, when the vehicle in the throttle after the anti-skid, and sometimes found that the flow meter signal voltage of 0.55V or so, then the engine failure warning light will not light, When the air flow meter signal voltage in the moment will become 0.35V, the engine failure warning light will immediately light up. After careful observation, found that the car engine electronic control system-related data flow in the idle occasionally will show normal, indicating the possibility of air flow meter damage is not.