Bad fuel tank breather valve?

I was driving home today sitting at a red light and all of a sudden my (DCT) car stalled. The tach needle did not bounce or do anything crazy, it just dropped to zero. My gas tank was slightly above 1/4 tank. It started back up on the first try and I drove to the gas station to fill up. Left the gas station and sat at another red light with no issues. Pulled into my driveway and when I had almost stopped moving it dipped pretty low, gave a bit of a shake then went back to normal. I let it sit for a minute at idle and no other problems. I was able to kind of replicate the problem by revving it up a little bit and letting off, but it took 4 or 5 tries. (Here's a video: https://vid.me/hEBI) There is a check engine light, but that's from no cats + coilovers. I ran carly bmw diagnosis and those were the only codes showing up. About a year ago I had the bouncing tach needle that ended up stalling right after I filled up but haven't had it since. And I know there is this thread with a great DIY to fix that problem: http://www.m3post.com/forums/showthread.php?t=1273927.

So to get to the point, I would like opinions on whether you guys think this is related to that or if it's more serious and related to the idle control valve? Or should I just stop whining and pay the ~$90 to try the breather fix first?

M3MPH1S wrote

I was driving home today sitting at a red light and all of a sudden my (DCT) car stalled. The tach needle did not bounce or do anything crazy, it just dropped to zero. My gas tank was slightly above 1/4 tank. It started back up on the first try and I drove to the gas station to fill up. Left the gas station and sat at another red light with no issues. Pulled into my driveway and when I had almost stopped moving it dipped pretty low, gave a bit of a shake then went back to normal. I let it sit for a minute at idle and no other problems. I was able to kind of replicate the problem by revving it up a little bit and letting off, but it took 4 or 5 tries. (Here's a video: https://vid.me/hEBI) There is a check engine light, but that's from no cats + coilovers. I ran carly bmw diagnosis and those were the only codes showing up. About a year ago I had the bouncing tach needle that ended up stalling right after I filled up but haven't had it since. And I know there is this thread with a great DIY to fix that problem: http://www.m3post.com/forums/showthread.php?t=1273927.

So to get to the point, I would like opinions on whether you guys think this is related to that or if it's more serious and related to the idle control valve? Or should I just stop whining and pay the ~$90 to try the breather fix first?

I don't think it's fuel tank breather. The tach should bounce after a full up . And maybe stall. But usually happens after a fill up to full.

Had happen once or twice in 4 years, shrugged it off. Time it did happen was right after a gas fill though, but so rare never worried about it.

Ive seen random stalling be caused by the vent valves before

GMWNashville wrote

Ive seen random stalling be caused by the vent valves before

What kind of vent valves? You mean the AC?

Fuel tank vent valve

What was the problem on your car? Did you solve the problem? I got same problem like you.

Did you find out the issue on your car? I got same problem as you..... could you help me?

GMWNashville wrote

Fuel tank vent valve

going to try this out. ive been having the same problems even after changing th DMTL or whatever its called.

anyone else change this and it fix the problem?

M3MPH1S is looking for your help

Just realized it's already been a year since I posted this

Hey so yeah I went ahead and finally bought the fuel tank breather valve a few weeks ago, but I haven't had time to change it yet. But since the original post, I've never had it stall again and only a few times have I had the bouncing needle, so it was low priority. I will try to get this repaired soon and report back.

My car has sort of a similar issue, except no stalls.
Idle bounces around a bit (between 700 and 1000 RPM) after filling up the tank and during the first start at a gas station.
Also my idle is not consistent - some days it's 550 RPM, some days it's 750.
Going to change out the fuel breather valve some time this spring, will report if it makes a difference.

When I had it repaired, the charcoal canister was replaced as well. No issues at all since then.

notouching wrote

My car has sort of a similar issue, except no stalls.
Idle bounces around a bit (between 700 and 1000 RPM) after filling up the tank and during the first start at a gas station.
Also my idle is not consistent - some days it's 550 RPM, some days it's 750.
Going to change out the fuel breather valve some time this spring, will report if it makes a difference.

My car sometimes exhibits the same thing. Normally my car idles at 800~RPM but sometimes it goes as low as 500RPM.

However if I let go of the brake pedal, it idles normally at 800~RPM.

Mine is DCT - it has never stalled.

Please keep us posted!

marcster wrote

My car sometimes exhibits the same thing. Normally my car idles at 800~RPM but sometimes it goes as low as 500RPM.

However if I let go of the brake pedal, it idles normally at 800~RPM.

Mine is DCT - it has never stalled.

Please keep us posted!

It’s supposed to idle 525-550. It sounds like you have a failing brake booster

So yeah, probably obvious, but just for followup I did replace the breather valve back in April 2018 (and again did a poor job of following up on my own post) and it fixed the issue.