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Mini Cooper R56 Idle Issues and Engine Stalling

Hello everyone, I own a 2008 Mini Cooper R56 with the N12 naturally aspirated gasoline engine (120 hp, non-turbo) and a mileage of 150,000 km. Ever since I bought the car, I’ve been experiencing an issue with the idle that still hasn’t been resolved. When I first start the engine (cold start), the idle fluctuates significantly. The car starts shaking like it's about to stall. The idle drops too low, then it revs up by itself again. After the engine warms up, the problem continues in a different way — for example, while waiting at a red light, the idle suddenly drops to around 450–500 rpm and then climbs back up again. About 2,000 km ago, I had a full engine and transmission rebuild, but the problem existed before the rebuild and still persists afterward. Almost every sensor and component related to idle and air-fuel mixture has been either replaced or tested. Still, the problem hasn’t gone away. It’s becoming so frustrating that I’m genuinely starting to lose all enthusiasm for the car. Has anyone experienced something similar? What could be the possible cause? I’d appreciate any help or suggestions. I'm honestly exhausted from chasing this issue.

A 2008 Mini Cooper R56 with a naturally aspirated N12 engine is experiencing persistent idle issues and engine stalling, despite a recent engine and transmission rebuild. The problem includes fluctuating idle during cold starts and low idle at traffic stops. Various components, including sensors, throttle body, and PCV system, have been replaced or tested without resolving the issue. Suggested solutions include checking the timing chain and tensioner for wear or improper tension, as these could affect engine performance and idle stability.

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17 comment(s)

Check the throttle body for carbon buildup or dirt, as this can affect idle stability. Cleaning the throttle body might help resolve the issue. Let me know if this makes any difference or if you have any further questions.

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Check the throttle body for carbon buildup or dirt, as this can affect idle stability. Cleaning the throttle body might help resolve the issue. Let me know if this makes any difference or if you have any further questions.

The throttle body was replaced with a new one. The problem is not caused by this.

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The throttle body was replaced with a new one. The problem is not caused by this.

Inspect the vacuum lines for any leaks or cracks, as vacuum leaks can cause erratic idle behavior. Pay special attention to the intake manifold gasket and any hoses connected to it. Let me know if you find anything unusual or if you have more questions.

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Inspect the vacuum lines for any leaks or cracks, as vacuum leaks can cause erratic idle behavior. Pay special attention to the intake manifold gasket and any hoses connected to it. Let me know if you find anything unusual or if you have more questions.

Smoke tests were performed twice for leaks. No leaks were detected.

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Smoke tests were performed twice for leaks. No leaks were detected.

Consider checking the idle air control valve (IACV) for proper operation, as it regulates the engine's idle speed. A malfunctioning IACV can cause idle fluctuations. If you haven't already, cleaning or replacing it might help. Please update me on your findings or if you have further questions.

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Consider checking the idle air control valve (IACV) for proper operation, as it regulates the engine's idle speed. A malfunctioning IACV can cause idle fluctuations. If you haven't already, cleaning or replacing it might help. Please update me on your findings or if you have further questions.

Hello, there is no idle air control valve (IACV) in my r56 n12 engine vehicle.

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Hello, there is no idle air control valve (IACV) in my r56 n12 engine vehicle.

Check the engine's PCV (Positive Crankcase Ventilation) system for any blockages or malfunctions. A faulty PCV valve can cause idle issues. Ensure that the valve and related hoses are in good condition. Let me know if this helps or if you have any other questions.

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Check the engine's PCV (Positive Crankcase Ventilation) system for any blockages or malfunctions. A faulty PCV valve can cause idle issues. Ensure that the valve and related hoses are in good condition. Let me know if this helps or if you have any other questions.

Since the engine was recently overhauled, the top cover gasket (and therefore the PCV valve) and PCV hoses were recently changed.

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Since the engine was recently overhauled, the top cover gasket (and therefore the PCV valve) and PCV hoses were recently changed.

Inspect the mass airflow sensor (MAF) for any dirt or malfunction, as it plays a crucial role in managing the air-fuel mixture. Cleaning the MAF sensor with a dedicated cleaner might improve the idle stability. Please let me know if this helps or if you have any further questions.

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Inspect the mass airflow sensor (MAF) for any dirt or malfunction, as it plays a crucial role in managing the air-fuel mixture. Cleaning the MAF sensor with a dedicated cleaner might improve the idle stability. Please let me know if this helps or if you have any further questions.

MAF sensor, oxygen sensors, camshaft position sensors, vanos solenoid valves were all replaced. Almost many sensors were renewed.

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