VW Caddy Engine Stalling: IAC Valve Troubleshooting

I had a similar issue with my VW Golf 2017 last winter. Having some experience with VAG engines, I initially thought it was just the IAC valve acting up like yours. The main symptoms matched exactly, unstable idle, stalling engine, and everything running smoother at higher RPMs. After scanning, the error codes pointed to air intake issues. Took it to my regular workshop where they found heavy contamination in the entire air intake system, particularly around the air valve assembly. The carbon deposits were restricting proper airflow, causing the idle control system to malfunction. They did a thorough cleaning of the intake manifold, replaced the IAC valve, and performed a recalibration of the idle settings. Total cost was 425€ for parts, labor and diagnostic work. Since then, the idle has been rock solid with no more stalling issues. Before suggesting specific fixes for your Caddy, could you share: Engine size and type, Current mileage, When was the last time you had a major service, Any modifications to the intake system, What error codes are you getting exactly This would help determine if your issue is similar to what I experienced or if there might be other factors at play.

Last service was completed at 12500km with no issues reported. Since then the car has only done about 600km. The error codes show P0505 and P0506, which points to the idle air control system. Given all symptoms match your experience, I will get the air intake system inspected for carbon buildup. A full system cleaning sounds like a reasonable first step before replacing parts. My vehicle has the stock intake setup, no modifications at all. Thanks for sharing the repair details and costs, helps set expectations for the workshop visit.

Thanks for the error codes, P0505 and P0506 are definitely classic symptoms of idle control issues. After seeing these same codes on my Golf, I had the workshop do a thorough inspection of the throttle body area first before jumping to parts replacement. Since your mileage is relatively low, carbon buildup might not be as severe as what I encountered. However, the idle speed problems can also be caused by a failing throttle position sensor or electrical issues in the idle control circuit. In my case, the workshop started with a thorough cleaning service of the throttle body and intake manifold which cost around 150€. While this improved things temporarily, the stalling engine problem returned after a few weeks. Only after replacing the idle control valve did the issue resolve completely. Given your car is newer with lower mileage, I would recommend: 1. Starting with a professional cleaning service 2. Having them test the electrical connections to the idle control components 3. Only proceeding with parts replacement if the problem persists This stepped approach helped avoid unnecessary parts replacement in my experience with the same engine family.

Thanks for the clear suggestions. I should mention the engine is a 2.0 TDI with 13100km on the clock. You make a good point about taking a staged approach, starting with cleaning before replacing parts makes sense, especially given the low mileage. The idle speed issues only started recently, and the stalling happens mainly when the engine is fully warmed up. I will ask the workshop to focus on the throttle body cleaning and electrical testing first. The 150€ estimate for a thorough cleaning service sounds reasonable. If that does not fix the idle control problems, at least we will have ruled out carbon deposits as the cause before looking at component replacement. I will book the car in next week and update once I know what they find. The error codes matching your experience gives me some confidence we are looking in the right direction for a solution to the engine stalling.