VW Passat TDI Stalling: Idle Control Valve Mystery

Had almost the same issue with my 2005 VW Golf TDI. The car engine idle was very unstable and it kept dying at traffic lights, which was really frustrating. After trying basic fixes like cleaning the throttle body myself, I finally took it to a workshop. They ran diagnostics and found the air intake system was heavily contaminated, restricting proper airflow at idle. The idle control was affected because of carbon buildup throughout the intake manifold. They had to do a thorough cleaning of the entire intake system and reset the idle control parameters. The complete service cost me 425€, including diagnostics and cleaning. Since then, the engine idle has been stable and the check engine light hasn't come back. Before suggesting specific fixes for your Passat, could you share: Current mileage, When was the last time you had the intake system cleaned, Any other symptoms besides the unstable idle, What error codes are you getting These details would help determine if your issue is similar and whether you might need the same type of service. With diesel engines, intake contamination is pretty common and can definitely cause these idle problems.

Had almost the same issue with my 2005 VW Golf TDI. The car engine idle was very unstable and it kept dying at traffic lights, which was really frustrating. After trying basic fixes like cleaning the throttle body myself, I finally took it to a workshop. They ran diagnostics and found the air intake system was heavily contaminated, restricting proper airflow at idle. The idle control was affected because of carbon buildup throughout the intake manifold. They had to do a thorough cleaning of the entire intake system and reset the idle control parameters. The complete service cost me 425€, including diagnostics and cleaning. Since then, the engine idle has been stable and the check engine light hasn't come back. Before suggesting specific fixes for your Passat, could you share: Current mileage, When was the last time you had the intake system cleaned, Any other symptoms besides the unstable idle, What error codes are you getting These details would help determine if your issue is similar and whether you might need the same type of service. With diesel engines, intake contamination is pretty common and can definitely cause these idle problems.

Had almost the same issue with my 2005 VW Golf TDI. The car engine idle was very unstable and it kept dying at traffic lights, which was really frustrating. After trying basic fixes like cleaning the throttle body myself, I finally took it to a workshop. They ran diagnostics and found the air intake system was heavily contaminated, restricting proper airflow at idle. The idle control was affected because of carbon buildup throughout the intake manifold. They had to do a thorough cleaning of the entire intake system and reset the idle control parameters. The complete service cost me 425€, including diagnostics and cleaning. Since then, the engine idle has been stable and the check engine light hasn't come back. Before suggesting specific fixes for your Passat, could you share: Current mileage, When was the last time you had the intake system cleaned, Any other symptoms besides the unstable idle, What error codes are you getting These details would help determine if your issue is similar and whether you might need the same type of service. With diesel engines, intake contamination is pretty common and can definitely cause these idle problems.

Thanks for sharing your experience with the intake system. My Passat had its last major service 6 months ago, and yes, my symptoms match exactly what you described. The error codes point to an IAC valve malfunction, specifically P0505. I already verified the throttle body is clean, as that was my first thought too. The engine stalling issues started gradually over the past month, especially noticeable when the engine is cold. Since my car only has 83572km on the clock, I was surprised to face these idle problems so soon after the service. The mechanic didnt mention any intake issues during the last checkup. Maybe I should get a second opinion from another shop about the idle control system?

Thanks for sharing your experience with the intake system. My Passat had its last major service 6 months ago, and yes, my symptoms match exactly what you described. The error codes point to an IAC valve malfunction, specifically P0505. I already verified the throttle body is clean, as that was my first thought too. The engine stalling issues started gradually over the past month, especially noticeable when the engine is cold. Since my car only has 83572km on the clock, I was surprised to face these idle problems so soon after the service. The mechanic didnt mention any intake issues during the last checkup. Maybe I should get a second opinion from another shop about the idle control system?

Thanks for sharing your experience with the intake system. My Passat had its last major service 6 months ago, and yes, my symptoms match exactly what you described. The error codes point to an IAC valve malfunction, specifically P0505. I already verified the throttle body is clean, as that was my first thought too. The engine stalling issues started gradually over the past month, especially noticeable when the engine is cold. Since my car only has 83572km on the clock, I was surprised to face these idle problems so soon after the service. The mechanic didnt mention any intake issues during the last checkup. Maybe I should get a second opinion from another shop about the idle control system?

Based on your mileage and symptoms, I think you might be dealing with a different issue than what I had. While my Golf's problems were solved by cleaning the air intake system, your P0505 code specifically points to the idle air control valve, and the timing after your service is suspicious. When my intake system was contaminated, the buildup happened over years, not months. Since your throttle body is clean and the problems started suddenly after service, I would actually check if something was overlooked or disturbed during the recent maintenance. In my case, before going for the full intake cleaning, I had similar idle speed problems that turned out to be a wiring issue near the IAC valve, a connector had worked loose during routine maintenance. The mechanic had accidentally knocked it while working on something else. Cost me just 85€ to fix once they found the actual problem. Given your car's low mileage and recent service, I would suggest: Have someone check the IAC valve connections first, Verify the idle speed settings were properly reset after the service, Get the IAC valve tested specifically, since the error code directly relates to it This could save you from an unnecessary full intake system cleaning, which might not address your specific issue.

Based on your mileage and symptoms, I think you might be dealing with a different issue than what I had. While my Golf's problems were solved by cleaning the air intake system, your P0505 code specifically points to the idle air control valve, and the timing after your service is suspicious. When my intake system was contaminated, the buildup happened over years, not months. Since your throttle body is clean and the problems started suddenly after service, I would actually check if something was overlooked or disturbed during the recent maintenance. In my case, before going for the full intake cleaning, I had similar idle speed problems that turned out to be a wiring issue near the IAC valve, a connector had worked loose during routine maintenance. The mechanic had accidentally knocked it while working on something else. Cost me just 85€ to fix once they found the actual problem. Given your car's low mileage and recent service, I would suggest: Have someone check the IAC valve connections first, Verify the idle speed settings were properly reset after the service, Get the IAC valve tested specifically, since the error code directly relates to it This could save you from an unnecessary full intake system cleaning, which might not address your specific issue.

Based on your mileage and symptoms, I think you might be dealing with a different issue than what I had. While my Golf's problems were solved by cleaning the air intake system, your P0505 code specifically points to the idle air control valve, and the timing after your service is suspicious. When my intake system was contaminated, the buildup happened over years, not months. Since your throttle body is clean and the problems started suddenly after service, I would actually check if something was overlooked or disturbed during the recent maintenance. In my case, before going for the full intake cleaning, I had similar idle speed problems that turned out to be a wiring issue near the IAC valve, a connector had worked loose during routine maintenance. The mechanic had accidentally knocked it while working on something else. Cost me just 85€ to fix once they found the actual problem. Given your car's low mileage and recent service, I would suggest: Have someone check the IAC valve connections first, Verify the idle speed settings were properly reset after the service, Get the IAC valve tested specifically, since the error code directly relates to it This could save you from an unnecessary full intake system cleaning, which might not address your specific issue.

Thanks everyone for the suggestions. After checking the IAC valve connections as recommended, I found the issue. There was indeed a loose connector that must have been disturbed during the last service. The repair shop admitted they had moved several components to access the timing belt area during the service. They fixed the connection free of charge since it was related to their previous work. The idle control is now working perfectly and the engine maintains a steady idle. The check engine light cleared after they reset the system. Total cost ended up being 0€ since it was covered under their service warranty. Much better than paying for unnecessary air intake cleaning or IAC valve replacement. My Passat is running smoothly again, maintaining proper idle speed at all stops. For anyone else facing similar idle problems right after a service, definitely check those connections around the throttle body and IAC valve first. Sometimes the simplest explanation is the correct one.

Thanks everyone for the suggestions. After checking the IAC valve connections as recommended, I found the issue. There was indeed a loose connector that must have been disturbed during the last service. The repair shop admitted they had moved several components to access the timing belt area during the service. They fixed the connection free of charge since it was related to their previous work. The idle control is now working perfectly and the engine maintains a steady idle. The check engine light cleared after they reset the system. Total cost ended up being 0€ since it was covered under their service warranty. Much better than paying for unnecessary air intake cleaning or IAC valve replacement. My Passat is running smoothly again, maintaining proper idle speed at all stops. For anyone else facing similar idle problems right after a service, definitely check those connections around the throttle body and IAC valve first. Sometimes the simplest explanation is the correct one.

Thanks everyone for the suggestions. After checking the IAC valve connections as recommended, I found the issue. There was indeed a loose connector that must have been disturbed during the last service. The repair shop admitted they had moved several components to access the timing belt area during the service. They fixed the connection free of charge since it was related to their previous work. The idle control is now working perfectly and the engine maintains a steady idle. The check engine light cleared after they reset the system. Total cost ended up being 0€ since it was covered under their service warranty. Much better than paying for unnecessary air intake cleaning or IAC valve replacement. My Passat is running smoothly again, maintaining proper idle speed at all stops. For anyone else facing similar idle problems right after a service, definitely check those connections around the throttle body and IAC valve first. Sometimes the simplest explanation is the correct one.