Hi.
My 2017 F55 3 cylinder with 90,000 miles has a check engine light that won't stay cleared.
Codes are P0440, Evap Emission System, and P0171, System Too Lean
Occasionally the engine will idle high (2000 rpm); a blip on the throttle brings it down, but then it comes up again. It does not do this all the time.

I checked the gas cap, but did not replace it.
I checked the purge vent valve; the solenoid valve works but won't hold a vacuum supplied by a MityVac, which I believe it should; cleaning attempt failed.
I've ordered a new vent valve. It'll be a few days before the valve arrives from across the country, I'm sure.
Could a leaky vent valve also cause the P0171 code? I'm thinking uncontrolled (edit: unmetered) air getting in via the valve and through the gas cap, which lets in air when a certain vacuum is reached (which it should as the gas level goes down).

Am I on the right track?

 

Sounds like that should be it, but doesn't hurt to check your airbox to make sure the hoses haven't come loose somehow.

 

Today, just when sitting idling in the garage, the rpms climbed to 2000. Blipping the throttle brought it down for a little while, and then it came back up to 2000 again.

I had an idea: I disconnected the tube from the tank into the purge control valve, and blocked off that inlet of the control valve (and hence the vacuum). My theory was that I would get only one error code for the Evap System, and nothing for lean mixture, which could be vacuum related. And...it worked: only the P0440 (evap) code and no climbing idle.

Now, just waiting for the purge valve.

 

The valve came in today, part# 13-90-7-621-174. Took 5 minutes to install. Cleared code, drove 73 miles. Code did not come back and it shows ready for emissions test.
I'm saying it was a success.

 

I am getting the same errors, and seem to have a similar issue. Where do you get to the part to replace it? Is there a book or website you would recommend that would show how to get to things like this?

 

I think I got the part from ECS, https://www.ecstuning.com/b-genuine-...e/13907621174/ .

It's been awhile, but the part is VERY easy to get to...it's right up front.
If you did your troubleshooting, and you're pretty sure that's it, if you buy the part, you'll see where it is...it's right up front.
It seems to be a fairly common problem with BMWs and there are YouTube videos on it..

 

Just an update: We carry it from bosch now at a lower price. https://www.ecstuning.com/b-bosch-pa...907621174~bos/