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Problem with the Mini R56 N12 engine


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Although rather verbose, my daughter has a 2008 Mini One Auto equipped with a 1.4 (N12) engine.

Everything was functioning well until last week when she arrived at a roundabout and the vehicle abruptly stopped moving (no problems or difficulties had occurred before this). In summary, I started the process by increasing the engine's speed at the beginning and successfully operated it to its destination (since she is a novice driver). While operating the vehicle, the power delivery seems to be within the expected range, devoid of any unpleasant sounds or excessive rev surges. However, upon halting the vehicle, the idle revs exhibit a lack of smoothness and appear to decrease slightly below the desired level. Consequently, the engine may attempt to abruptly cease its operation. The start-up process is as described before. Once the engine is heated, it requires a few revs to elevate the idle speed beyond its stuttering. After this, the engine will continue to operate smoothly until you cease. It consistently starts up on the first attempt, regardless of whether the engine's speed decreases and it stalls.

Fortunately, I have a buddy who is skilled in mechanics, and we have made several attempts to address this issue, but have not achieved any success so far.

Initially, it is seen that the engine management light remains inactive throughout the duration of the problem. Initially, there were two failure codes identified: one for the downstream oxygen sensor and another for mass air flow, which is a conceivable possibility.

We initiated the resolution of several prevalent problems. We replaced the four coil packs, as they had not been replaced in the service history. We also examined the camshaft sensors and replaced the o2 sensor, which resolved the fault code. Additionally, we conducted a thorough search for vacuum leaks. Despite visual inspection, no damage was found. Furthermore, we applied a generous amount of brake cleaner and observed no change in the engine's rotational speed.

Subsequently, we examined the throttle body. We believed we had identified the problem in this case, since the gasket had a little crimp. We successfully obtained a second-hand body and replaced both the body and gasket. The service history indicated that the body had been cleaned in 2019, suggesting that it may not have been properly reinstalled at that time. Upon replacing the aforementioned component, the Mass air flow error warning was thereafter eliminated. thereafter, we have operated the vehicle several times without any recurrence of the aforementioned message. We used the Service menu to reacquaint ourselves with the idle state after the replacement of items. Nevertheless, the engine continues to experience rough idle and stalling, despite the absence of any problem codes to investigate.

I am inquiring if anybody has had a similar issue with a N12 engine and has any recommendations for other sources to explore. He has indicated that we should examine for any potential chain stretch, but we have not yet explored that possibility. I am interested in identifying any further common faults that may be contributing to the situation at hand.

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Which scanning tools were used to identify codes? It is important to note that not all scanning tools can detect all codes. Various factors may contribute to the issue at hand, such as timing chain issues, malfunctioning vanos systems, cracks in the PCV pipe from the rocker cover to the intake manifold, and idling effects. The only method to address these issues is via a smoke test.

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It is quite likely that he uses an Autel MaxiSys device. I engaged in conversation with him earlier today, and we want to do a smoke test either tomorrow or Thursday in order to observe the results.

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The number of 60,000 miles should be regarded as a round figure. It is important to note that guides may break extremely often after a decade of use. Additionally, it is necessary to do oil pressure tests while the engine is hot. A healthy engine operating at 105°C at idle should typically have a pressure of about 20 psi, while a healthy engine should have a pressure of 40 psi at 3000 rpm.

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We will examine it. Conducted a smoke test today and saw significant leakage from the cam cover, with no indications of any other issues. Upon removal, the gaskets exhibited severe damage, displaying brittleness and a tendency to shatter upon removal. It seems that the inside components have been heated. After replacing all the gaskets and doing a brief test drive, the vehicle originally seemed satisfactory. However, as it reaches high temperatures, the issue of rough idle and stalling resurfaces. (PS - The chain guide was visually OK when we removed the lid today).

However, I also encountered some new problems today. During a somewhat extended test drive, I had a misfire characterised by a substantial emission of white exhaust smoke. Additionally, the vehicle exhibited a decrease in power upon being pulled away after a prolonged period of driving. Tomorrow, I will re-examine the vehicle using a fault reader to see if any other issues have arisen. However, I have not observed any indications of engine warning lights.

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If the timing chain has been used for over 60,000 miles, it will require a replacement. Additionally, remove the oil control solenoid for valves and clean the gauze filters on them. Perform a smoke test on the pcv pipe before reinserting it into the inlet manifold. If smoke is observed coming from below the pipe, it is likely to be broken and will result in various idle issues. If the pipe becomes stuck, I will inspect it and remove any obstructions.

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Thank you for your assistance, Mistral. There seemed to be a sense of terminality after today's journey. The car is now emitting oil from its exhaust system. We have made the decision to cease further expenditure on it and will shortly list it on eBay as a non-runner.

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