BMW; Throttle opening; Intake vacuum degree; correlation

It is a common problem of N55 engine that the correlation between throttle position and intake manifold pressure exceeds the limit value.

The fault code means that the intake manifold pressure and throttle position do not match. In the N55 engine, the intake is controlled by the valve lift, so the throttle valve does not control the intake volume, but only controls the pressure in the intake manifold-usually kept at a negative pressure of 50mbar. The throttle opening and the obtained negative pressure have preset values (expected correlation) in the computer. If the actually measured throttle opening+intake manifold vacuum does not match the expected value, this fault code will be recorded. The main source of the problem is air leakage. The components most likely to leak air are the front and rear oil seals of the crankshaft and the crankcase ventilation device in the cylinder head cover.

Throttle is a controllable valve, which is used to control air to enter the engine. After entering the intake pipe, it is mixed with gasoline (different models of cars have different design mixing parts) to become combustible mixture, which participates in combustion and does work. Four-stroke gasoline engines are generally like this. Throttle is the most important component in EFI automobile engine system. Its upper part is the air filter, and the lower part is the engine block, which is the throat of the automobile engine. Whether the acceleration of a car is flexible is closely related to the cleanliness of the throttle. Whether the throttle should be removed for cleaning is also the focus of discussion among car owners.