What causes to diesel engines to idle a bit rough?

Diesel engines may idle roughly due to several factors, including fuel quality issues, such as contaminated or low-grade diesel fuel. Additionally, problems with the fuel injectors, such as clogging or malfunction, can lead to uneven fuel delivery. Mechanical issues, such as worn engine components or improper timing, can also contribute to a rough idle. Lastly, air intake restrictions or exhaust system blockages can affect engine performance, resulting in an unstable idle.