Скачать или смотреть Nissan NV350 E26 | Engine knocking noise at idle

*Main Complaints Received:*
1. Engine knocking noise at idle, with the RPM needle fluctuating between 700 and 1200 RPM.

We have successfully remedied the automatic door issue; however, we are still actively troubleshooting the engine-knocking complaint.

#### Detailed Troubleshooting Steps:

1. *Initial Analysis of Fuel Flow Data:*
We meticulously examined the data related to fuel flow, focusing on several components: the injector pump, suction control valve (SCV), rail limiter valve, and fuel pressure sensor. This foundational analysis guided our subsequent testing efforts.

2. *Injector Maintenance:*
*Injector Removal:* All four injectors were carefully removed for servicing. Upon inspection, we noted significant carbon buildup in the third injector bay due to backfire, requiring the use of specialized tools for retrieval.
*Cleaning and Calibration:* Each injector underwent a thorough cleaning followed by recalibration before reinstallation.
*Chamber Preparation:* Before reinserting the injectors, a specialized tool was employed to ensure the chamber was adequately sheathed.
*Testing Results:* Unfortunately, reinstalling the original injectors did not alleviate the knocking noise.

3. *New Injector Testing:*
We procured and tested a brand-new set of injectors. Despite our expectations, the knocking noise persisted.

4. *Component Replacements:*
*Suction Control Valve and Rail Limiter Valve:* Both were replaced with reconditioned and new parts, yet the issue remained unaddressed.
*Fuel Pressure Sensor:* This component was also replaced, but it did not impact the engine behavior.
*Complete Fuel Rail System:* We replaced the entire fuel rail system, but no change in engine performance was observed.

5. *Engine Performance Evaluations:*
*Compressor Tests:* Conducted thorough engine compression tests across all cylinders, with each confirming satisfactory compression levels.
*Reconditioned Injector Pump:* A reconditioned injector pump was installed, resulting in a reduction in white smoke emissions, although the knocking sound persisted but reduced to 30%

6. *Injector Pump Servicing:*
The original injector pump has been sent to DIMO for professional servicing as of last Friday, October 25, 2024.

7. *Fuel System Cleaning:*
The fuel tank was removed for a complete cleaning, including a thorough check of the filter and fuel lines, to eliminate any potential blockages.

8. *Exhaust System Maintenance:*
The entire exhaust system was cleaned, which included cutting and removing carbon deposits that may contribute to engine performance issues.

9. *Key Component Replacements:*
*Throttle Body Replacement:* This was done to ensure proper air intake management.
*O2 Sensor Replacement:* The oxygen sensor was replaced to optimize combustion.
*Air Mass Sensor:* A new air mass sensor was installed to improve airflow monitoring.
*Turbocharger Service:* The turbocharger was removed, serviced, and reinstalled, including maintenance of the intercooler.
*Intake System Maintenance:* The complete intake system was also removed, cleaned, and then reinstalled to ensure optimal performance.

10. *Timing Chain Inspection:*
A comprehensive check of the timing chain kit—which comprises 15 components—was conducted. We identified slight stretching in the secondary (top) timing chain. While this is not critical enough to prevent the engine from starting, we decided to reinstall the original components for further testing.

11. *ECU Communication:*
We reached out to the ECU filer supplier to inquire about the original ECU file. Unfortunately, they were unable to provide the original files, prompting us to cease communication with them. (attached is the communication thread)
Simultaneously, we collaborated with an alternative company to acquire the latest version of the ECU file. We took the following steps in the ECU programming process:
Successfully flashed the existing tweaked ECU file.
Virginized the ECU to reset or restore it to factory settings.
Reinstalled a base original file.

12. *Current Status and Next Steps:*
As a result of the ECU adjustments, the engine knocking noise has been reduced by approximately 90%. Nonetheless, we are continuing to troubleshoot the remaining potential mechanical issues.
We have identified two critical areas for further investigation:
1. Replace the ECU with a new unit (currently searching for a suitable replacement).
2. Remove the engine head to inspect for any gaps between the inlet and exhaust valves, though this remains a tentative course of action pending confirmation of symptoms.

Conclusion:
We are committed to resolving these issues and will provide ongoing updates as we progress. Thank you for your patience as we work through these challenges.