Cleaning This BMW Part SAVED ME Big Time!

One sort of sketchy hiccup during my N52 BMW E90 ownership was a sudden misfire in two of the engine's six cylinders. The car threw a light (and a code) and lost significant power. The rough idle that came with the misfires was also greatly concerning. Disconnecting and reconnecting the battery didn't seem to remedy anything, and the spark plugs all looked good. Thankfully, after thoroughly researching the fault code, I found a cleaning procedure that ended up saving the day! Here's the procedure that saved me a trip to the dealership (and a big bill):

Located at the front of the engine, just below the engine cover are two VANOS solenoids. VANOS stands for “Variable Nockenwellen Steuerung,” which is a variable valve timing technology developed by BMW. The two solenoids can be seen here:

We'll need to pull the air intake ducting out of the way for better access to the solenoids.

Two get the intake ducting out of the way we need to remove two T20 torx screws located on either side of the ducting.

After removing the two torx screws, we can disconnect the ducting from the intake box and remove the ducting.

Removing the ducting improves our view of the solenoids. Both solenoids are secured with a 10mm bolt. The VANOS intake solenoid is above, the exhaust solenoid is directly below it.

Removing the 10mm bolt allows us to pull the solenoid from the engine.

The VANOS solenoid electrical connection can be disconnected by pressing the metal spring clip here.

Be sure to retain the rubber o-ring pictured above. It can sometimes get stuck in the engine. As seen in the picture, this solenoid was quite dirty inside.

Engine degreaser or brake clean can be used to clean the solenoid. I opted to use engine degreaser.

After soaking the solenoid with a cleaner, thoroughly blow out the cleaner and any remaining debris using compressed air.

With our solenoid and o-ring cleaned, we can lubricate the o-ring with some clean motor oil and reinsert the solenoid. 

With the solenoid fully inserted, we can reinstall the 10mm bolt and torque to 7 ft-lbs (9 Nm). The VANOS electrical connection can also be reconnected at this time.

Now all that's left to do is reinstall our intake ducting and the two T20 torx screws.

Cross your fingers and fire her up!

In the case of this car's misfires and rough idle, both were fully resolved with this simple cleaning procedure! This process won't remedy a rough idle and/or misfires in all situations but is certainly worth a shot if you encounter VANOS or misfire codes. For an even more thorough cleaning, the (lower) exhaust solenoid can also be removed and clean. This engine was only throwing an intake solenoid code and a quick cleaning proved to be all it needed! I hope others can use this helpful tip to resolve issues too, avoiding a trip to the dealership!

Best of luck and happy motoring,

—JD