Why is the system too lean at idle in the Tiguan?

[SilasAnn]

For the Volkswagen Tiguan, the possible causes of a lean air-fuel mixture at idle include an intake system air leak or incorrect air-fuel ratio. Both of these issues can lead to the P2178 code (System Too Lean at Idle) in the Tiguan. Below are detailed explanations of the potential causes: Intake System Air Leak: An air leak in the intake system can result in a lean air-fuel mixture. It is recommended to check whether the oil dipstick is properly inserted, inspect the oil cap seal for aging, and examine if the PCV valve is damaged. Incorrect Air-Fuel Ratio: An incorrect air-fuel ratio can also cause a lean air-fuel mixture. It is advisable to check if the throttle body is dirty or clogged, as dirt can lead to a lean mixture. Additionally, inspect whether the fuel injectors are atomizing properly. For models equipped with the EA888 engine, cleaning the fuel injectors is recommended since direct injection engine injectors are difficult to remove and inspect. If no issues are found, check the engine control unit for any fault codes related to the oxygen sensor. If none are present, it is suggested to read the data stream again to confirm and rule out oxygen sensor faults.