Assistance is requested. Limited performance

[Adv3nture]

The vehicle in question is a 2012 Range Rover Supercharged with an AJ133 engine. It has accumulated a mileage of 165,000 km.
Hello, I shall endeavour to provide a comprehensive amount of info in this article. This is my first personal Rover, having previously worked on several others without encountering this particular difficulty.
During first startup, the engine operates in an uneven manner and results in limited performance. However, after it reaches the optimal operating temperature and I reset the error codes, it functions flawlessly. The engine exhibits a significant amount of tapping noises, however it has been reported that this is within the expected range of operation.
During frigid temperatures, the high pressure fuel sensor indicates a reading of 54 psi. However, as the temperature increases, the sensor registers a range of 2000-2400 psi.
At this juncture, the limited performance notification ceases to appear and the system functions optimally.
DTC P00108-0 indicates a permanent high input in the MAP/Barometric sensor.
P0088-00 is a pending historic code. The fuel pressure is too high. There is a pending fault code P0087-00 indicating that the fuel pressure is too low.
P0300 indicates the presence of pending random misfires.
The codes P0301-P0308 Engine misfires occur on all cylinders.
P0316 indicates a misfire that occurs at the startup of the engine.
Any assistance would be very appreciated; I would much prefer not to randomly replace components without a clear solution.

[CrownChikk]

My first hypothesis would be a deteriorating High-Pressure Fuel Pump (HPFP). The device will not operate at such a low pressure.
If one of the High-Pressure Fuel Pumps (HPFPs) is malfunctioning, I recommend replacing both of them.
However, in order to prevent randomly replacing components, it is advisable to examine the issue more closely. Another possible reason might be a malfunctioning injector, but in such cases, there would typically be some noticeable emission of petrol from the exhaust.

[Adv3nture]

I much appreciate your assistance.

[BuffUpdate]

I had a same issue with my 2010 vehicle. The cause of the issue was the timing chain. A slack chain might result in misfire codes since it disrupts the accurate timing. To assess the slackness of the chain tension, just loosen the oil filler cap and delicately manipulate it in an upward and downward motion with a screwdriver. If it seems excessive, it will be removed or eliminated quickly. Should be snug with little looseness. Hopefully, this information proves beneficial.

[Adv3nture]

It seems that the issue lies in the fact that the high-pressure fuel pump (HPFP) was changed, but the problem persisted. However, when inspecting the timing chain, it was seen to be excessively worn. Fortunately, I possess the necessary skills to do the task of replacing the timing chain, although it will need a significant amount of time. I appreciate all the assistance provided! Upon inspection, it was seen that the timing chain was excessively loose. The automobile was then used until it reached a warm temperature, during which it performed well. Subsequently, the timing chain was reexamined and found to be securely tightened. What are your thoughts?

[Bridgenix]

If the chain was loose initially, it is quite probable that it remains loose, however I cannot provide information on its tightness. I recall using a diagnostic programme to reset the error codes, and I saw that on some occasions, the issue would not resurface for a distance of 20 miles, but on other occasions, it would reoccur instantly. Consider taking it to the dealer and paying a diagnostic price of $150 to accurately identify the problem before taking further action.

[Adv3nture]

Currently, I am excluding timing as a potential culprit since after the vehicle has reached its optimal operating temperature, it functions normally. However, after parking the car and attempting to start it again, these error codes appear. Upon observation, I have seen that the battery voltage drops below 12 when this issue occurs. I have previously changed both the battery and alternator. Could a battery drain be the reason of this issue?

[Adv3nture]

[Bridgenix]

Eliminate the possibility of a battery problem by charging the battery slowly and continuously until it reaches full capacity overnight, and then attempt to start the device.

I had a problem on my Audi S5 where many odd TCM and other errors appeared due to a defective ECU, causing me significant distress.

If you are capable, I recommend opting for a diagnostic fee of $150. This way, you can be certain about the issue at hand and, given your proficiency, you may do the task alone.

[Adv3nture]

That is an excellent suggestion. Thank you for sharing it. I will definitely use it.

[Bridgenix]

The ECU also provided me with codes indicating low voltage.

[Adv3nture]

The possibility of a battery issue has been eliminated. However, I have discovered an observation that may provide a clue in the correct direction. When recording the live data during a cold start, the fuel pressure on the rail reads 570kpa with the key on. After starting the engine and experiencing misfiring and a decrease in performance when accelerating, the fuel pressure only fluctuates between 530-600kpa. Furthermore, when I press the throttle, the fuel pressure drops down to 400kpa. Considering that fuel thickens when cold due to its oil-based nature, it is plausible that the issue lies with either the in-tank pump or the filter.

[Bridgenix]

I recommend inspecting both the fuel filter and fuel pump. If the pressure is enough when the key is inserted, but the engine loses power when the accelerator is pressed, it indicates a potential obstruction in the fuel filter or fuel pump.

[Adv3nture]

Very well, I will proceed to substitute the pump and filter and observe the outcome.

[engrol]

Greetings, have you discovered the resolution?

[Adv3nture]

The issue was ultimately caused by the timing of the fuel pumps, which had become misaligned. After performing the necessary timing adjustment, the engine has been working reliably ever since.