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The year 2007 The Mini Cooper S is experiencing misfiring issues after uphill driving.


Uneripty

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Today, while driving my 2007 Cooper S (automatic), I encountered a significant incline that stretched for around one mile. I was travelling at a speed of approximately 55-60 miles per hour. Approximately one-fourth into the ascent, I detect an anomaly, like a failed attempt by the gearbox to change gears. Subsequently, at around the midpoint of the incline, the engine began experiencing vibrations and decelerating.

I successfully ascended the hill and proceeded to go a few further kilometres till I reached a petrol station. The engine operated well until when I engaged 6th gear in manual mode, at which point it would resume shaking. Upon arriving at the petrol station and coming to a halt, the engine exhibited significant trembling.

Fortuitously, I had my diagnostic tool readily available in the rear compartment. Consequently, I connected it and retrieved the following error codes:

    The following diagnostic trouble codes (DTCs) have been detected: - 2A56: Oxygen Sensor Heating After Catalyst (CAT) Function - 2777: Combustion Misfire in Cylinder 3 - 2D52: Digital Motor Electronics (DME) Super Knocking 2DCD - Fuel Shutoff Caused by Excessive Knocking in Cylinder 3 2781 - Multiple Cylinder Misfire During Combustion
    2771 - Cylinder 1 experiencing combustion misfire. 2775 - Cylinder 3 experiencing combustion misfire. 277D - Cylinder 2 experiencing combustion misfire.

I reset the error codes, adjusted the scanner settings to display misfires for each individual cylinder, started the engine, and promptly saw misfiring, mostly occurring in cylinder 2, but cylinders 1 and 4 were also affected.

After a period of contemplation, I decided to transport it back to my residence by driving.

When I analysed the data using the scanner, I saw that there was no misfire occurring over 3,200 rpm. However, when the engine speed dropped below this threshold, cylinder 4 exhibited severe misfiring. Additionally, while the vehicle was moving at a very slow pace, all cylinders were experiencing a significant level of misfiring.

Upon arriving home, I reexamined the codes and found that they merely displayed the following:

    2781 - Multiple cylinders experiencing combustion misfire.
    Error code 2775 indicates a combustion misfire in cylinder 3.
    The diagnostic trouble codes are as follows: 2771 - Cylinder 1 combustion misfire 277D - Cylinder 2 combustion misfire

I have not conducted any inquiry beyond examining the codes. I am completely clueless on where to begin. Possible causes might include timing issues, compression issues, valve issues, and so forth.

Any guidance would be much appreciated. Thank you!

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Ascending a slope puts significant strain on the engine. The throttle is in a more open position, allowing for a greater volume of air to enter the cylinders. Additionally, the compression pressure inside the cylinders is increased. A greater level of pressure, together with the breadth of the spark plug gap, need an increased voltage from the ignition coil in order for the spark to successfully traverse the gap. If the high voltage is able to establish an alternate route to the ground, such as via the spark plug insulator or by bypassing a plug wire, it will result in a misfire of the spark plug.

It is recommended to replace spark plugs after covering a distance of 50,000 kilometres. Begin at that point. To determine whether the issue is resolved, I would recommend replacing the outdated plugs. If not, it is possible that the issue is in the ignition coils, which might be malfunctioning. If the spark plugs have been faulty for an extended period, the ignition coils have likely been strained due to the need to provide high voltage for those malfunctioning plugs, resulting in impaired coil performance.

If the issue does not stem from an ignition problem, the next likely culprit would be a fuel pressure problem. Insufficient pressure or volume in the high pressure fuel injectors will result in unsuccessful combustion. If this were true, I would anticipate that you would have encountered fuel trim issue codes, which you did not specify.

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Thank you for your reply, I get the explanation. The vehicle has accumulated a mileage of 151,000 kilometres. The information on the previous replacement of the plugs is unknown. I will extract them, assess their appearance, and undoubtedly substitute them. This task is rather straightforward and likely necessitates their replacement. Indeed, you are accurate in stating that there are no codes pertaining to fuel, save for the one that triggers fuel cutoff as a result of engine knocking. However, this code is not associated with pressure in any way.

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A new set of spark plugs will temporarily address the issue of misfires until the excessive oil consumption and fuel mixture imbalance cause another set of plugs to fail. It is now time to do a maintenance refresh.

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Indeed, I have seen the presence of soot on the back part. The automobile belongs to my sister, although I sometimes drive it while she is at school.

What would you suggest for a comprehensive refresh, such as a complete engine rebuild?

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The presence of overheating, oil residue, and discoloration in the form of white or black deposits on the rings, stem seals, timing chain, and plugs indicates potential issues. Greyish brown residue is considered healthy, while black residue suggests a rich fuel mixture. Bright white residue with melted electrodes indicates a lean running condition and burning oil. Such conditions can lead to excessive heat, making the rings brittle. In turbo engines, this can potentially cause a hole to melt in the hottest cylinder, typically located near the gearbox end.

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What kind of fuel does it contain? The knock sensor activated at the first occurrence (at low revolutions and high load, which is a common situation).

I recommend resetting any error codes and filling the tank with the highest available octane fuel in your location. I am aware that the usage of lower octane fuels in high output engines might lead to complications.

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I would reconsider my previous statement and do a compression test on each individual cylinder. It is possible that you have previously had a pre-ignition incident, which is causing concern. The third plug is narrating a tale.

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Typically, the third or fourth cylinder is prone to melting in turbo engines due to a weak fuel mixture and excessive heat. This may also lead to severe knocking and poor performance when using gasoline with an octane rating lower than 98 RON, which is recommended for Cooper S engines.

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