Optimizing the performance and efficiency of a compression-ignition motor hinges on its smooth working. Yet, the emergence of harsh running in a diesel motor can give rise to genuine concerns. In this article, we will delve into the various factors that lead to a harsh-running compression-ignition engine, exploring eventual root causes. Moreover, we'll provide viable remedies to tackle these challenges effectively.


What causes a diesel engine to run rough

Frequent factors include blocked combustion strainers, defective nozzles, air leaks in the intake chain, low compression in toppers, contaminated diesel, or motor’s ignition system issues. 

Why does diesel engine running rough and shaking 

The fuel-air mixture may not be igniting correctly due to issues with combustion atomizers, inadequate squeeze in cylinders, or defective ignition timing. As a consequence, incomplete combustion leads to uneven power delivery, causing vibrations and shaking. Moreover, air leaks in the intake system can introduce surplus air, upsetting the optimal combustion mixture ratio. 


Why does a diesel engine runs rough on first start 

Within the initial ignition, a diesel motor might exhibit harsh operation. When the ignition process commences, the compression-ignition equipment may experience an imbalance, leading to its shaky performance, as seen with a "diesel engine running rough at idle." This roughness is attributed to factors such as inadequate combustion atomizing, insufficient squeeze in cylinders, or suboptimal ignition sequence set-up. It results in partial burning, causing uneven power delivery and vibrations during the engine's initial start-up.

Causes of rough idling in diesel engines

One frequent factor is the presence of air leaks in the engine's intake system, which disrupts the precise air-fuel mixture required for smooth combustion. Additionally, dirty or blocked fuel injectors lead to uneven fuel distribution, affecting the engine's productivity at motionless. Combustion quality and contamination issues, such as water or sediment in the diesel or gasoline, can also contribute to diesel engine sounds rough. Moreover, problems with the engine's pre-heaters or glow plug relay can hinder efficient ignition during cold starts, leading to roughness at idle. 

Diesel engine runs rough when warming up 

A diesel engine running rough when accelerating or during its warm-up phase due to several factors. One primary reason is the engine's fuel-to-air ratio being imbalanced during the initial stages of warming up or when demanding higher power output during acceleration. Diesel rough idle when warms or accelerates requires a specific air-fuel mixture for optimal combustion, and any deviation from this balance can lead to harsh running. Moreover, during acceleration, issues with the combustible system, such as clogged filters or injector problems, can disrupt combustion delivery, further exacerbating rough operation. Additionally, problems with the glow plugs or glow plug relay not functioning correctly can cause insufficient heat for effective ignition, contributing to roughness both during warm-up and acceleration. In some cases, a diesel engine running rough with white smoke, which can indicate potential fuel or injector issues that need attention. 


How to fix diesel engine rough running 

Fixing a rough running diesel engine involves a systematic approach to identify and address the underlying issues. Here are some steps to help you resolve the problem:

1. Diagnose the issue: perform a thorough inspection and diagnostic check to identify the specific cause of the rough idling diesel engine.

2. Check combustion quality: ensure that the diesel you are using is of good quality and free from contaminants. Water or impurities in the fuel can lead to rough running and other engine issues.

3.Inspect combustion filters and injectors: check and clean or replace clogged combustion filters, and inspect the fuel injectors for any blockages or malfunctioning. We recommend using BIZOL GDI POWER CLEAN. It can be filled directly into the fuel tank at every maintenance or every 10,000 km. This additive reduces deposit formation and increases nozzle life. For optimal cleaning of the entire fuel system, we also recommend using BIZOL Gasoline System Clean+ g80.uct-range. Faulty injectors can cause uneven fuel distribution, leading to rough engine operation.

4. Address air intake leaks: verify the integrity of the motor’s air intake system. 

5. Inspect glow plugs: for motors equipped with glow plugs, check their functionality. 

6. Check compression levels: conduct a compression test to assess the motor’s health and identify potential cylinder issues.

7. Inspect ignition system: ensure that the motor’s ignition system is functioning correctly.

8. Perform regular maintenance: regularly service and maintain the diesel motor, including oil changes, filter replacements, and overall inspections. 

9. Seek professional help: if you are unsure about the problem or unable to diagnose and fix it yourself, consider seeking assistance from a qualified mechanic.


By following these steps and addressing the specific causes of diesel engine rough idle, you can restore your diesel engine to smooth and efficient operation. 


Gasoline System Clean+ g80
Gasoline System Clean+ g80 250ml
Gasoline System Clean+ g80 250ml
Gasoline System Clean+ g80
  • cleans injectors efficiently  

  • removes carbon deposits from intake valves and combustion chamber 

  • increases the octane number and performance of engine

  • reduces fuel consumption and lowers emissions  

  • extends the life of the fuel system

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