Engine speed waviness at idle in BMW – how to fix it?

BMW driver question

There are minimal rpm undulations at idle. Sometimes it is all OK, normal and the pointer stands still. The engine runs evenly and sitting inside the car there is no body shake. I drive longer routes on premium fuel. The filters have been replaced. What could be the cause?

The problem affected a BMW E90 320d 07.2005 model, but it also happens in other models.

Engine in BMW 5 E60

Response from BM Cars service

The symptoms described can be associated with a great many faults. Replacement of filters and good fuel alone will not solve all the problems associated with engine revving. It is necessary to thoroughly diagnose the fuel, injection and exhaust systems with a special analysis of the patency of the DPF filter.

After a mileage of about 200,000 kilometers, or earlier if the car is operated for short distances, the particulate filter becomes “clogged”, resulting in an increase in exhaust gas pressure and the effect of engine shuddering, rev ripple or even power loss. We have coveredthe topic of cleaning the diesel particulate filter before in our tips.

We invite you to take advantage of our service.

BMW E90 | By Rudolf Stricker (Own work)[GFDL or CC-BY-SA-3.0], via Wikimedia Commons

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BMW E90 | By National Highway Traffic Safety Administration (File, Description) [Public domain], via Wikimedia Commons

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BMW E90 | By OSX (Own work) [Public domain], via Wikimedia Commons