How to Solve High Idle Speed in Tiguan Engine?

[SophiaRose]

The factors causing high idle speed in the engine are as follows: 1. The throttle body is dirty, with carbon deposits and gum affecting the normal return of the throttle, causing it to close intermittently. 2. Faults in the air flow sensor or throttle position sensor and their circuits. 3. Battery is undercharged. 4. Vacuum hose leaks or intake manifold gasket is damaged and leaking, PCV (Positive Crankcase Ventilation) valve core does not return properly, functioning intermittently. 5. Valves do not close tightly. Below are the solutions for high idle speed in the engine: 1. Check the throttle opening. For most electronically controlled engines, when the engine reaches normal temperature and the idle valve is fully closed, the basic idle speed is set to 500±50r/min. If the basic idle speed is too high, check the vacuum sealing of the system, especially the sealing of the vacuum tube, PCV valve, and crankcase-related parts. 2. Check the engine load signal. At this time, connect the idle control valve. Under normal engine operating temperature, its opening should be between 15%-25%. If the idle control valve opening is too large, check whether the engine load signal is normal, such as the air conditioning signal, battery voltage, and the temperature value of the water temperature sensor. 3. Check the vacuum degree of the intake manifold. Under normal engine idle conditions, the vacuum degree of the intake manifold should be 57-71kPa. If the vacuum degree is too low, it will cause abnormal pressure signals in the engine intake system, and the engine computer will mistakenly think the load has increased, thereby increasing the idle speed. 4. Reset the engine computer. Resetting the engine computer means clearing the fault memory in the engine computer and letting it relearn the idle speed. 5. Check whether the throttle is fully closed during idle and whether the throttle cable is stuck. Push the throttle lever in the closing direction. If the engine idle speed can drop to the normal speed, it means the throttle is stuck and does not close tightly. If the throttle cable is stuck, replace the cable. If the throttle shaft is stuck, disassemble and clean the throttle body. 6. Readjust the idle speed program according to the specified procedure of the engine. If the adjustment is ineffective, further inspection is required. 7. Check for leaks at the intake system pipe joints, vacuum hoses, etc. 8. Perform fault self-diagnosis. If there is a fault code, find the cause of the fault according to the displayed fault code.

[Val]

I've encountered the issue of high idle speed with my Tiguan, which is quite concerning because high idle not only increases fuel consumption and costs but may also lead to engine overheating or disturbing noise. Start with the basics: check if the throttle body is dirty or stuck, remove it and spray with a specialized cleaner for cleaning; if there's an air leak in the intake system, such as loose hose connections, use soapy water to locate and seal the leak. I also found that faulty sensors like the coolant temperature sensor or mass airflow sensor can cause the ECU to misjudge and raise the idle speed, so reading the OBD fault codes for diagnosis is helpful. If that doesn't work, try resetting the ECU: disconnecting the battery for 10 minutes and then reconnecting can sometimes resolve software bugs. But safety first—don't force yourself to perform operations you're not comfortable with. It's best to promptly visit a 4S shop or professional repair shop for a comprehensive inspection to prevent the problem from worsening. Don't risk daily driving safety over minor issues.