528i – CCV system and Idle Control Valve

I’m chasing a stumble that happens at idle when the car is cold. Once the car is warmed up it runs fine, but while it’s warming up it sometimes stumbles and dies at a stop light.

Last weekend I replaced the entire crankcase ventilation system. That consists of an oil separator unit and a handfull of hoses.

The difficulty lays in the fact that the separator is stuffed way up under the intake manifold. Luckily you can get under there and replace it without removing the manifold.

There are a series of videos from Bavarian Autosport that show the procedure, and that is pretty much what I did. The videos are for a different model, but they are pretty close.

Here is a photo showing where the CCV separator is located. I’ve already removed the air filter, mass air flow sensor, idle control valve, intake manifold adjuster (DISA) valve, throttle body, and unplugged a bunch of connectors to get a wiring harness out of the way.



Here is a closer view showing the two screws that hold in the CCV oil separator.


While I was in there I also removed and cleaned the throttle body. It was filthy, I doubt it’s ever been cleaned.



Much better after cleaning.


Here are the old CCV parts. They are kind of busted up because it’s easier to get them out that way.


These are the new parts. You might notice that the oil separator and hoses look different. That’s because the new ones are a “cold weather” version – they have insulation to prevent any water vapor from freezing and causing issues. It also made them a little more difficult to install.



A lot of the work is done “blind” – you just kind of put your hands up under the manifold and connect stuff up. Luckily all the hoses just kind of “clip” on. But the new o-ring seals were pretty stiff, so it was still a pain in the ass.

I also replaced the throttle body seal and one of the air hoses that looked like it was starting to crack.

I had ordered a new idle control valve, but it didn’t arrive in time for installation last weekend.

After replacing the CCV system the car seemed to run the same. Not better, but not worse. I also cleared all the codes and cleaned and applied dielectric grease to all the electrical connectors that I removed, and the spark plug connectors. No new codes have appeared yet.

Today I installed the new idle control valve – it went much faster this time.

On the test drive it still dipped the rpms a bit at the stops, but not quite as much, and the engine did not die. So it appears to be better.

I guess I’ll drive it this week and see what we see.

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