What to do if the Audi Q5 idles rough without fault codes?
2 Answers
Idling roughness is generally an engine issue. Roughness during cold starts is mostly caused by poor fuel combustion. Long-term poor combustion will definitely lead to carbon deposits, but it cannot be concluded that poor combustion necessarily means a large amount of carbon deposits. At the very least, it indicates that the fuel system should be cleaned or the fuel should be changed. Dirty air filter: The air filter is designed to protect the engine and reduce wear. It is usually replaced around 10,000 kilometers. If not replaced in time, insufficient air intake can cause low idle speed, leading to engine roughness. Clogged fuel injectors: Fuel injectors are key components for fuel injection in cars and have a long service life, reaching hundreds of thousands of kilometers. However, gums in gasoline can clog the injector nozzles, causing inconsistent fuel injection among the injectors. This results in uneven operation of each cylinder, leading to engine roughness.
Idle speed vibration without any fault codes can indeed be quite frustrating. My Q5 had the same issue before. It turned out to be carbon buildup – after running 30,000 km without cleaning, the throttle body was covered in black sludge when opened up. Spraying it with specialized cleaner for half an hour and then taking it for a couple of high-speed runs fixed the problem. However, it could also be due to worn engine mounts – German car rubber components are particularly prone to sagging. Listen for any knocking sounds in the engine bay during cold starts. If you still can't identify the issue, I suggest checking the fuel line pressure as fuel pump pressure leaks can cause unstable fuel supply. One last trick: try running a full tank of 98-octane fuel – some owners have cured their vibration issues this way.
