What is the fault of the unstable idle speed of Audi a4l in 2009? Why 850 and 750?

The main reasons of unstable idle speed and jitter;

1, the most common cause of vehicle jitter is that the throttle valve is too dirty or the fuel injector has too much carbon deposit.

2. When there is too much carbon deposit in the engine, the gasoline sprayed by the fuel injection head will be absorbed by the carbon deposit during cold start, which leads to too thin mixture during cold start and difficult start. In this case, only when the gasoline absorbed by carbon deposits is saturated can it easily enter the car.

3. After landing, the gasoline adsorbed on the carbon deposit will be sucked into the cylinder by the vacuum suction of the engine for combustion, so that the mixture will be enriched, and the combustible mixture of the engine will be diluted and concentrated, resulting in idling jitter after cold start. The lower the temperature, the more oil is needed for cold start, and the existence of carbon deposit will affect the smooth start.

The serious idle vibration is generally caused by engine cylinder missing, rubber aging or loosening, carbon deposition, fuel system failure and other reasons.

Solutions;

The best way is to clean the oil circuit, clean it regularly and use fuel additives such as PNF stock solution to solve the above problems caused by carbon deposition. The poor quality of fuel or the long storage time of fuel in the initial stage of a new car will lead to the rapid increase of colloidal components in the oil circuit, which will continuously pollute the fresh fuel, resulting in no good fuel to participate in the combustion in the later stage, and the carbon deposition exceeds the standard, especially for the national six cars. Only by maintaining a clean oil circuit can most problems be gradually alleviated.