VW Golf TDI Stalling: IAC vs Throttle Body Issues

Had the same symptoms on my 2011 VW Passat TDI. The idle speed would fluctuate out of nowhere and the engine kept stalling, especially after cold starts. Initial diagnosis revealed heavy carbon buildup in the intake manifold and throttle body, affecting the IAC valve operation. The contamination was preventing proper air flow regulation at idle. These TDI engines are prone to this issue due to their EGR system. The fix required a complete intake cleaning service. The throttle body and IAC valve were removed, and all passages were professionally cleaned to remove carbon deposits. The idle control system needed recalibration after cleaning. This was a serious issue that required immediate attention, as continued operation could have led to more severe engine problems. After the service, the idle speed stabilized completely and the stalling stopped. Would recommend getting it checked soon, as carbon buildup only gets worse over time. Make sure to find a shop experienced with VW TDI engines since proper cleaning requires specific knowledge and tools. The check engine light in your case likely indicates a fault code related to the idle control system or throttle position sensor, which matches these symptoms.

I had exact same symptoms with my Golf TDI last year. The engine stalling at idle and rough idle speed turned out to be heavy carbon deposits in the air intake system. Had to get a full cleaning service done on the intake manifold, and they found the air valve was pretty badly gunked up too. The repair totally fixed the stalling issues and irregular idle. The engine runs really smooth now. Just curious, did you end up getting yours fixed? What was the final cost of the repair job? Have you had any other related problems come up since the work was done? Would be good to know for future reference.

Thanks for asking about the repair outcome. Since seeing the mechanic last month, they confirmed the bad idle air control valve was causing the stalling engine issues. The intake system was heavily contaminated, requiring thorough cleaning and valve replacement. The total repair came to 425€, which included cleaning all intake components and installing a new IAC valve. The car idle is now perfectly stable with no stalling problems. The engine maintains steady RPMs at all temperatures, and the check engine light has stayed off. The air intake system cleaning made a noticeable difference in overall engine performance. After 3000km of driving since the repair, no related issues have surfaced. Regular maintenance should prevent future carbon buildup affecting the engine idle control. For preventive care, the mechanic suggested using high-quality fuel and scheduling intake cleanings every 40000km to avoid similar problems developing again.

After dealing with my stalling engine problems, I finally got everything sorted out. Took it to a reputable VW shop where they did a complete diagnosis. Just like they suggested, the IAC valve was completely clogged with carbon deposits, making the car idle really rough. The mechanic showed me the gunked-up parts, it was pretty bad. They did a thorough cleaning of the entire intake system and replaced the air valve. Total bill came to 450€, but the difference in how the engine runs now is night and day. No more stalling issues and the idle is perfectly smooth. Been driving it for about a month now and all systems are working great. The check engine light has stayed off and engine performance is solid. The shop recommended regular intake cleanings to prevent future buildup, which makes sense given how bad it got. Really glad I got it fixed when I did, the mechanic mentioned waiting longer could have caused bigger problems. Worth every penny to have a properly running engine again.