VW Up Stalling: Bad IAC Valve Causes Unstable Idle

Had a similar issue with my 2013 VW Polo TSI. The engine would stall during idle speed, especially after cold starts. Initially thought it was a minor issue but the car kept stalling at traffic lights. With some car repair experience from working on my previous vehicles, I first checked for obvious issues but ultimately needed professional help. The workshop diagnosed a heavily contaminated throttle body and intake system, which was causing irregular idle speeds and the check engine light. The complete service included cleaning the throttle body, air valve assembly, and intake manifold. Total cost was 425€ including parts and labor. Since the repair, the idle speed has been perfectly stable and no more stalling issues. Before suggesting specific solutions, could you share: Current mileage on your Up, When was the last throttle body cleaning done, Are there any other symptoms besides engine stalling, Does the problem occur more frequently when the engine is cold or warm This information would help determine if your issue matches what I experienced. While IAC valve issues can cause similar symptoms, contaminated intake systems are also common culprits for unstable idle problems.

After 86940km and regular maintenance, I can confirm the IAC valve was indeed the problem. The workshop identified significant carbon buildup affecting the idle speed control. They also found the throttle body needed cleaning. The repair involved replacing the IAC valve and performing a thorough throttle body cleaning. Total cost was 380€. The engine idle is now perfectly stable with no stalling issues, even during cold starts. For others experiencing similar symptoms, having both components checked saved time and prevented recurring problems. The stable idle and smooth operation confirmed this was the right fix.

Thanks for the detailed follow-up about your VW Up repair. Your experience matches what I found with my Polo, these idle control issues often involve multiple related components. Had my throttle body cleaned too while fixing the idle problems. The carbon buildup you mentioned affecting the IAC valve is quite common in these engines. The 380€ repair cost seems reasonable considering both the valve replacement and throttle body service. My repair was slightly more expensive at 425€ since they also cleaned the intake manifold. The stable idle after fixing both components confirms what many of us have learned, when dealing with stalling engine issues, checking the entire idle control system rather than just one part often prevents future problems. Your preventive approach of addressing both the IAC valve and throttle body was smart. Have you noticed any improvement in overall engine response besides the stable idle? My Polo felt noticeably smoother overall after the cleaning work was done.

After 86940km and regular maintenance, I can confirm the IAC valve was indeed the problem. The workshop identified significant carbon buildup affecting the idle speed control. They also found the throttle body needed cleaning. The repair involved replacing the IAC valve and performing a thorough throttle body cleaning. Total cost was 380€. The engine idle is now perfectly stable with no stalling issues, even during cold starts. For others experiencing similar symptoms, having both components checked saved time and prevented recurring problems. The stable idle and smooth operation confirmed this was the right fix. Thanks for all the responses. The car runs remarkably better overall, not just at idle speed. The engine response is crisper and the car feels more responsive when accelerating from a stop. Will definitely keep a closer eye on these components during future maintenance to prevent similar issues. Would recommend anyone with similar stalling engine symptoms to have both the IAC valve and throttle body inspected rather than assuming its just one component. The combined service ended up being the most cost-effective solution.