RS3 Power Loss & Rough Running Due to Lean Condition

As someone with moderate experience working on performance cars, I dealt with nearly identical symptoms on my 2021 RS4. The check engine light came on followed by rough running and power loss. After diagnostic testing, a faulty fuel injector was identified as the root cause. The injector wasnt delivering the correct fuel spray pattern, leading to incomplete combustion and a lean condition. The mass air flow sensor readings confirmed the lean mixture. The repair involved: Complete fuel injector testing, Replacement of one defective injector, Cleaning of remaining injectors, Full system diagnostic scan, Test drive verification Total cost was 515 Euro for parts and labor. The symptoms completely disappeared after repair and fuel economy actually improved slightly. To better assist with your situation, could you share: Any specific error codes from the check engine light? Does the rough running occur more at idle or under load? Have you noticed any changes in fuel consumption? Any recent maintenance or modifications? The oxygen sensor readings would also be helpful to confirm if its running lean consistently or only under certain conditions. This could point to whether its an injector issue like mine or potentially something else in the fuel delivery system.

As someone with moderate experience working on performance cars, I dealt with nearly identical symptoms on my 2021 RS4. The check engine light came on followed by rough running and power loss. After diagnostic testing, a faulty fuel injector was identified as the root cause. The injector wasnt delivering the correct fuel spray pattern, leading to incomplete combustion and a lean condition. The mass air flow sensor readings confirmed the lean mixture. The repair involved: Complete fuel injector testing, Replacement of one defective injector, Cleaning of remaining injectors, Full system diagnostic scan, Test drive verification Total cost was 515 Euro for parts and labor. The symptoms completely disappeared after repair and fuel economy actually improved slightly. To better assist with your situation, could you share: Any specific error codes from the check engine light? Does the rough running occur more at idle or under load? Have you noticed any changes in fuel consumption? Any recent maintenance or modifications? The oxygen sensor readings would also be helpful to confirm if its running lean consistently or only under certain conditions. This could point to whether its an injector issue like mine or potentially something else in the fuel delivery system.

As someone with moderate experience working on performance cars, I dealt with nearly identical symptoms on my 2021 RS4. The check engine light came on followed by rough running and power loss. After diagnostic testing, a faulty fuel injector was identified as the root cause. The injector wasnt delivering the correct fuel spray pattern, leading to incomplete combustion and a lean condition. The mass air flow sensor readings confirmed the lean mixture. The repair involved: Complete fuel injector testing, Replacement of one defective injector, Cleaning of remaining injectors, Full system diagnostic scan, Test drive verification Total cost was 515 Euro for parts and labor. The symptoms completely disappeared after repair and fuel economy actually improved slightly. To better assist with your situation, could you share: Any specific error codes from the check engine light? Does the rough running occur more at idle or under load? Have you noticed any changes in fuel consumption? Any recent maintenance or modifications? The oxygen sensor readings would also be helpful to confirm if its running lean consistently or only under certain conditions. This could point to whether its an injector issue like mine or potentially something else in the fuel delivery system.

As someone with moderate experience working on performance cars, I dealt with nearly identical symptoms on my 2021 RS4. The check engine light came on followed by rough running and power loss. After diagnostic testing, a faulty fuel injector was identified as the root cause. The injector wasnt delivering the correct fuel spray pattern, leading to incomplete combustion and a lean condition. The mass air flow sensor readings confirmed the lean mixture. The repair involved: Complete fuel injector testing, Replacement of one defective injector, Cleaning of remaining injectors, Full system diagnostic scan, Test drive verification Total cost was 515 Euro for parts and labor. The symptoms completely disappeared after repair and fuel economy actually improved slightly. To better assist with your situation, could you share: Any specific error codes from the check engine light? Does the rough running occur more at idle or under load? Have you noticed any changes in fuel consumption? Any recent maintenance or modifications? The oxygen sensor readings would also be helpful to confirm if its running lean consistently or only under certain conditions. This could point to whether its an injector issue like mine or potentially something else in the fuel delivery system.

Thanks for all the feedback. After getting error codes read, P0171 confirmed the lean condition. The rough running is definitely worse under load during acceleration. The oxygen sensor readings are showing consistently lean across different RPM ranges. Last service was at 195000 KM, mainly routine maintenance. One detail I forgot to mention, there is a subtle whistling noise from the intake manifold area when accelerating. The throttle body was cleaned during the last service but no other work was done to the intake system. The mass air flow sensor readings look normal based on the scan data. The spark plugs were also replaced during that last service interval. Still trying to narrow down if this is a vacuum leak or fuel delivery problem before taking it in.

Thanks for all the feedback. After getting error codes read, P0171 confirmed the lean condition. The rough running is definitely worse under load during acceleration. The oxygen sensor readings are showing consistently lean across different RPM ranges. Last service was at 195000 KM, mainly routine maintenance. One detail I forgot to mention, there is a subtle whistling noise from the intake manifold area when accelerating. The throttle body was cleaned during the last service but no other work was done to the intake system. The mass air flow sensor readings look normal based on the scan data. The spark plugs were also replaced during that last service interval. Still trying to narrow down if this is a vacuum leak or fuel delivery problem before taking it in.

Thanks for all the feedback. After getting error codes read, P0171 confirmed the lean condition. The rough running is definitely worse under load during acceleration. The oxygen sensor readings are showing consistently lean across different RPM ranges. Last service was at 195000 KM, mainly routine maintenance. One detail I forgot to mention, there is a subtle whistling noise from the intake manifold area when accelerating. The throttle body was cleaned during the last service but no other work was done to the intake system. The mass air flow sensor readings look normal based on the scan data. The spark plugs were also replaced during that last service interval. Still trying to narrow down if this is a vacuum leak or fuel delivery problem before taking it in.

Thanks for all the feedback. After getting error codes read, P0171 confirmed the lean condition. The rough running is definitely worse under load during acceleration. The oxygen sensor readings are showing consistently lean across different RPM ranges. Last service was at 195000 KM, mainly routine maintenance. One detail I forgot to mention, there is a subtle whistling noise from the intake manifold area when accelerating. The throttle body was cleaned during the last service but no other work was done to the intake system. The mass air flow sensor readings look normal based on the scan data. The spark plugs were also replaced during that last service interval. Still trying to narrow down if this is a vacuum leak or fuel delivery problem before taking it in.

Appreciate the additional details. The whistling noise you mentioned immediately caught my attention, as I experienced this exact symptom with my RS4 before the injector issue surfaced. However, given your description of the noise location and the recently cleaned throttle body, this could point to a vacuum leak in the intake manifold. The P0171 code combined with the consistent lean condition across RPM ranges typically suggests either a vacuum leak or fuel delivery problem. While my issue was fuel injector related, your symptoms sound more characteristic of a vacuum leak, especially with that whistling noise. The mass air flow sensor readings being normal is actually helpful in narrowing this down. When my injectors were failing, the mass air flow sensor readings were erratic. The clean readings in your case further support the vacuum leak theory rather than a fuel delivery problem. Consider checking: Intake manifold gaskets for deterioration, PCV system components, Vacuum lines for cracks or loose connections, Intake manifold for hairline cracks The check engine light combined with these symptoms would make warranty coverage likely if thats still applicable. My repair experience was different since it was injector related, but vacuum leaks on these engines are a known issue that can cause identical problems.

Appreciate the additional details. The whistling noise you mentioned immediately caught my attention, as I experienced this exact symptom with my RS4 before the injector issue surfaced. However, given your description of the noise location and the recently cleaned throttle body, this could point to a vacuum leak in the intake manifold. The P0171 code combined with the consistent lean condition across RPM ranges typically suggests either a vacuum leak or fuel delivery problem. While my issue was fuel injector related, your symptoms sound more characteristic of a vacuum leak, especially with that whistling noise. The mass air flow sensor readings being normal is actually helpful in narrowing this down. When my injectors were failing, the mass air flow sensor readings were erratic. The clean readings in your case further support the vacuum leak theory rather than a fuel delivery problem. Consider checking: Intake manifold gaskets for deterioration, PCV system components, Vacuum lines for cracks or loose connections, Intake manifold for hairline cracks The check engine light combined with these symptoms would make warranty coverage likely if thats still applicable. My repair experience was different since it was injector related, but vacuum leaks on these engines are a known issue that can cause identical problems.

Appreciate the additional details. The whistling noise you mentioned immediately caught my attention, as I experienced this exact symptom with my RS4 before the injector issue surfaced. However, given your description of the noise location and the recently cleaned throttle body, this could point to a vacuum leak in the intake manifold. The P0171 code combined with the consistent lean condition across RPM ranges typically suggests either a vacuum leak or fuel delivery problem. While my issue was fuel injector related, your symptoms sound more characteristic of a vacuum leak, especially with that whistling noise. The mass air flow sensor readings being normal is actually helpful in narrowing this down. When my injectors were failing, the mass air flow sensor readings were erratic. The clean readings in your case further support the vacuum leak theory rather than a fuel delivery problem. Consider checking: Intake manifold gaskets for deterioration, PCV system components, Vacuum lines for cracks or loose connections, Intake manifold for hairline cracks The check engine light combined with these symptoms would make warranty coverage likely if thats still applicable. My repair experience was different since it was injector related, but vacuum leaks on these engines are a known issue that can cause identical problems.

Appreciate the additional details. The whistling noise you mentioned immediately caught my attention, as I experienced this exact symptom with my RS4 before the injector issue surfaced. However, given your description of the noise location and the recently cleaned throttle body, this could point to a vacuum leak in the intake manifold. The P0171 code combined with the consistent lean condition across RPM ranges typically suggests either a vacuum leak or fuel delivery problem. While my issue was fuel injector related, your symptoms sound more characteristic of a vacuum leak, especially with that whistling noise. The mass air flow sensor readings being normal is actually helpful in narrowing this down. When my injectors were failing, the mass air flow sensor readings were erratic. The clean readings in your case further support the vacuum leak theory rather than a fuel delivery problem. Consider checking: Intake manifold gaskets for deterioration, PCV system components, Vacuum lines for cracks or loose connections, Intake manifold for hairline cracks The check engine light combined with these symptoms would make warranty coverage likely if thats still applicable. My repair experience was different since it was injector related, but vacuum leaks on these engines are a known issue that can cause identical problems.

Thanks, this has been really helpful in understanding what might be going on. Going to book it in for service tomorrow and make sure they focus on checking for vacuum leaks given the symptoms. The whistling noise does seem to match what others have described with intake manifold issues. The car is definitely still under warranty, so hoping they can identify and fix the root cause quickly. Looking back, that whistling noise started before the other symptoms but I initially dismissed it. Pretty sure the air-fuel ratio being off ties back to air getting in where it shouldnt be rather than a fuel delivery problem. Will get the intake manifold and surrounding components thoroughly checked, especially since the throttle body work was done recently. The consistent lean readings make more sense now if its a vacuum leak rather than a failing fuel injector or mass air flow sensor issue. Appreciate everyone helping narrow this down, will update once I get the actual diagnosis.

Thanks, this has been really helpful in understanding what might be going on. Going to book it in for service tomorrow and make sure they focus on checking for vacuum leaks given the symptoms. The whistling noise does seem to match what others have described with intake manifold issues. The car is definitely still under warranty, so hoping they can identify and fix the root cause quickly. Looking back, that whistling noise started before the other symptoms but I initially dismissed it. Pretty sure the air-fuel ratio being off ties back to air getting in where it shouldnt be rather than a fuel delivery problem. Will get the intake manifold and surrounding components thoroughly checked, especially since the throttle body work was done recently. The consistent lean readings make more sense now if its a vacuum leak rather than a failing fuel injector or mass air flow sensor issue. Appreciate everyone helping narrow this down, will update once I get the actual diagnosis.

Thanks, this has been really helpful in understanding what might be going on. Going to book it in for service tomorrow and make sure they focus on checking for vacuum leaks given the symptoms. The whistling noise does seem to match what others have described with intake manifold issues. The car is definitely still under warranty, so hoping they can identify and fix the root cause quickly. Looking back, that whistling noise started before the other symptoms but I initially dismissed it. Pretty sure the air-fuel ratio being off ties back to air getting in where it shouldnt be rather than a fuel delivery problem. Will get the intake manifold and surrounding components thoroughly checked, especially since the throttle body work was done recently. The consistent lean readings make more sense now if its a vacuum leak rather than a failing fuel injector or mass air flow sensor issue. Appreciate everyone helping narrow this down, will update once I get the actual diagnosis.

Thanks, this has been really helpful in understanding what might be going on. Going to book it in for service tomorrow and make sure they focus on checking for vacuum leaks given the symptoms. The whistling noise does seem to match what others have described with intake manifold issues. The car is definitely still under warranty, so hoping they can identify and fix the root cause quickly. Looking back, that whistling noise started before the other symptoms but I initially dismissed it. Pretty sure the air-fuel ratio being off ties back to air getting in where it shouldnt be rather than a fuel delivery problem. Will get the intake manifold and surrounding components thoroughly checked, especially since the throttle body work was done recently. The consistent lean readings make more sense now if its a vacuum leak rather than a failing fuel injector or mass air flow sensor issue. Appreciate everyone helping narrow this down, will update once I get the actual diagnosis.