09 years 1.8T Passat 7W multi kilometers repair idle dithering, running up normal. Start looking at the random jitter of the engine, much like the jitter. The decoder reads the fault, and the display system is normal. Start reading data flow, throttle opening normal, idling jitter air flow changes larger, not well judged. The throttle is added to the 2000 turn engine and the intake air volume is basically normal. There is no problem on the computer, and it is suspicious of air leakage. Use carburetor cleaning agent to find leakage, and no air leakage is found. Will it be blocked? I didn't think of any good method, so I detected the intercooler. Business as usual! It is in trouble at this time. I wonder if turbocharging will be a problem. If there is a problem, should the intake data flow be wrong? Do not find the problem, first check and check, so start the car, unload the throttle door hose, + point oil throttle steady to 2000 turns, found that the hoses are not as big as other car feeling! When the throttle is reduced to 1200 turns, it is obvious that it feels unstable when it comes out. With this phenomenon, there is a goal. There is no problem with intercooler. That is intake, so there is no rest. Check the turbocharged intake, open the air filter, idle immediately stable! Air filter plugging? A blank filter is good, no matter the new installation, the cover above the cover, the idle speed gradually began to shake up and shake up, empty filter problem, then the empty filter box has a problem, take the light one empty filter shell filter net is all dust, clean up and remove the fault code. Business as usual! Idle speed turbocharging speed is low, suction is called small, resulting in idle speed when the intake is insufficient, idle speed jitter! This car is a rental company car, usually in the small market maintenance, no cleaning filter, I hope you see this post, meet the maintenance of the Passat on the air filter screen cleaning on the outer shell feeling!