Audi C5A6 equipped with 1.8T engine and automatic transmission, driving mileage of 50000 km. Car owners reflect the engine in 2,3 gear acceleration have abnormal noise, the abnormal noise has lasted about half a month's time, through the OBD Diagnostic Tool to check, the sound becomes apparent.
After testing, in 2, 3 block accelerated heard engine abnormal noise, listen to the voice really like engine knock, but the power of the engine were not affected by any effect, accelerate the engine sound all normal. Combined with the failure analysis, the engine at 2,3 gear acceleration can send different sound There are several reasons:
(1) variable valve timing mechanism fault. Because in the 2,3 gear acceleration engine has entered the medium-load conditions, according to the characteristics of the engine, the valve timing should have entered the adjustment position, adjust the mode by changing the position of the chain tensioner to achieve. According Launch X431 V Pro or Launch X431 IV GX4 tool check, found that when the chain camshaft adjustment, if the chain tensioner lack of strength will make the chain in a relaxed state in the adjustment process and beep.
(2) Since the engine knock sound is generated. That there are several possibilities: ① fuel octane low lead to knock. This car's engine may be use 93 unleaded gasoline, it is best to use 95 unleaded gasoline, otherwise it will produce detonation. ② ignition timing is premature detonation. To further understand the failure, you can use Autel MaxiScan MS509 or Autel MaxiScan VAG405 tools to detect, which can quickly check out the car parts problem.