What causes the BMW N52 engine to idle roughly?
2 Answers
The reasons for rough idling in the BMW N52 engine: 1. The throttle body is too dirty, excessive carbon buildup directly leads to unstable engine idle and poor acceleration, requiring throttle body cleaning; 2. Excessive carbon deposits inside the engine reduce combustion chamber volume, and the heat-absorbing properties of carbon deposits can cause incomplete combustion in the chamber, increasing the likelihood of knocking and engine vibration, necessitating internal engine carbon cleaning. BMW is a German luxury car brand, with model series including i, x, z, and pure numeric designations such as 1, 2, 3, 4, 5, 6, 7, and 8. Taking the BMW X5 as an example, it is the brand's first four-wheel-drive SUV model, with body dimensions of 4930mm in length, 2004mm in width, and 1776mm in height.
I've worked on quite a few BMW N52 engines, and rough idle is a pretty common issue. The most frequent cause is ignition system problems – things like worn spark plugs or faulty ignition coils can lead to misfires and noticeable shaking. Clogged fuel injectors are another major culprit, especially with inconsistent fuel quality in China causing carbon buildup that blocks injector nozzles and leads to uneven fuel delivery. Carbon deposits on valves and vacuum leaks are also common offenders, particularly when the crankcase ventilation valve or intake manifold gaskets age, destabilizing air intake at idle. Worn engine mounts will amplify the whole engine's vibration. My advice is to first read the trouble codes to check for misfires, then inspect wear items like spark plugs and coils, and finally investigate carbon buildup and sealing issues. Otherwise, minor problems can snowball into major repairs.
