Rough idle and loss of power when throttle is pressed down

Hello,

The BMW N55/54 engine is notorious for either blocked injectors or faulty coils/spark plugs.

For misfires, please swap coils and plugs between cylinders for initial testing.
Usually, the cause will be the injectors.

As you do not list any fuel pressure codes I would suggest to start with checking the spark plugs when you cross swap them. Check for any abnormal blackness, this would indicate faulty injector spray pattern. You can sent the injectors to a specialist shop for testing.

If you replace the injectors take note of the index number, see picture below.

Index 11 injectors must be replaced as a set. The fuel flow rate is considerably better than the previous versions and cannot be mixed in the engine with the older variants.
Index 06 †09 can be mixed together and anything before index 05 must be replaced.

After replacing injectors you will need to program the injector compensating values to the DME with a suitable diagnostic tool. The compensation number is circle in blue on the picture
You must also change the crushable washer. The cap covering the Teflon seal must be removed just before fitting the injector. The maximum time from the cap being removed is 10 mins. If left too long the seal will swell and may be damaged when fitting into the cylinder.

It is recommended that you replace the spark plugs together with the injectors.

It’s a good idea to clear the engine adaptations also. Over a period of time the engine ECU will try to adapt and fix known problems and may be masking further issues.

After replacement and adaptations reset a long 30 minute road test must be carried out to allow the adaptations to be relearned.

Please let us know how you get along.

Cheers, Boris