[CrimsonMoonLight72]

Tried searching for this but didn’t give exact info I needed. My 340i in the past has been topped off with gas a few times and idle would stumble a bit at first red light after filling up and 5 or so miles later it would stop and smooth out. No CEL ever btw.....

So awhile back I made sure never to top off again but despite no more top offs idle still stumbles occasionally at first stop after fill up. Is this more than likely the purge valve or the breather vent valve as far as a replacement t goes? I’ve heard some people use these 2 parts interchangeably when discussing my issue.

Also would it be worth it to plug into my bootmod3 to check to see if there is any codes despite no CEL? Something tells me the engine probably is pulling timing until the stumble goes away. Not sure though

[njdangelo]

Had the same problem. My problem was also accompanied by the fuel pump cutting off before the tank was actually full. Theres a few posts on here about it but i'm having a hard tine finding them now. Anyway, this solved my problem. No more post fill up stumbles.

https://www.turnermotorsport.com/BMW...tt=13907643106

[CrimsonMoonLight72]

Originally Posted by njdangelo

Had the same problem. My problem was also accompanied by the fuel pump cutting off before the tank was actually full. Theres a few posts on here about it but i'm having a hard tine finding them now. Anyway, this solved my problem. No more post fill up stumbles.

https://www.turnermotorsport.com/BMW...tt=13907643106

Yeah I figured that part as well but was told to first check to see what if any codes were thrown out. I logged in to my bm3 account plugged into car ( it’s been almost a year since I’ve done so ) and was able to run a diagnostic check. No codes! Nothing....so maybe the idle stumbles have to happen to a certain number of times for a code to appear? Idk if I should pay $100 for something that is not throwing a code!?!?

also apparently when you don’t log into bm3 for a long time I guess bootmod forgets your car and programs? After running diagnostics I tried clicking my maps and other functions and the screens were blank!! Before hooking into agent though I did receive a message about updating my agent?? No clue what that means or how to do it

[njdangelo]

Originally Posted by CrimsonMoonLight72

Yeah I figured that part as well but was told to first check to see what if any codes were thrown out. I logged in to my bm3 account plugged into car ( it’s been almost a year since I’ve done so ) and was able to run a diagnostic check. No codes! Nothing....so maybe the idle stumbles have to happen to a certain number of times for a code to appear? Idk if I should pay $100 for something that is not throwing a code!?!?

also apparently when you don’t log into bm3 for a long time I guess bootmod forgets your car and programs? After running diagnostics I tried clicking my maps and other functions and the screens were blank!! Before hooking into agent though I did receive a message about updating my agent?? No clue what that means or how to do it

I had no codes either. updating your agent is the bm3 software on your computer. to update it, click 'update' when on bootmod3.net

[CrimsonMoonLight72]

Originally Posted by njdangelo

I had no codes either. updating your agent is the bm3 software on your computer. to update it, click 'update' when on bootmod3.net

So just pony up and put it on without any codes or cel? I guess I could....but I hope the heck it solves the problem. Like I put it on and it still stumbles afterward. That would suck

[b58boi]

I have the exact same issue in a 16 340i. Did you ever resolve the issue?

[CrimsonMoonLight72]

Originally Posted by b58boi

I have the exact same issue in a 16 340i. Did you ever resolve the issue?

Yes....finally got the codes for tank ventilation....ordered a new tank breather valve which sits right on manifold. It’s pretty easy to replace apparently.

Too many gas fill up top offs caused this no,doubt.

[njdangelo]

Originally Posted by CrimsonMoonLight72

Yes....finally got the codes for tank ventilation....ordered a new tank breather valve which sits right on manifold. It’s pretty easy to replace apparently.

Too many gas fill up top offs caused this no,doubt.

I think letting the tank get too empty may actually effect it more but who knows. Glad you got it sorted. You should be able to replace it in about 3 minutes. easy as pie, just don't snap a hose or connector lol. They are plastic and not flexible.

[b58boi]

Originally Posted by njdangelo

I think letting the tank get too empty may actually effect it more but who knows. Glad you got it sorted. You should be able to replace it in about 3 minutes. easy as pie, just don't snap a hose or connector lol. They are plastic and not flexible.

I just replaced the tank breather valve and went straight to fill up about 5 miles away. Car still idles rough after a minute…. Talked to my shop and they told me to bring it in so they can reprogram the car. Did you have to reprogram anything after you replaced the part? I never got a CEL and scan shows no codes so there’s nothing to reset.

[njdangelo]

Originally Posted by b58boi

I just replaced the tank breather valve and went straight to fill up about 5 miles away. Car still idles rough after a minute…. Talked to my shop and they told me to bring it in so they can reprogram the car. Did you have to reprogram anything after you replaced the part? I never got a CEL and scan shows no codes so there’s nothing to reset.

Nope. Nothing to reprogram. Your rough idle is only present after filling right? My idle would normalize after 2-3 minutes after fill up. If your idle is rough continuously it's most likely something else.

[b58boi]

Originally Posted by njdangelo

Nope. Nothing to reprogram. Your rough idle is only present after filling right? My idle would normalize after 2-3 minutes after fill up. If your idle is rough continuously it's most likely something else.

Yes rough idle only present right after fill up. Once I drive for a good 5 minutes and I come to a stop there is no rough idle anymore. Very frustrating…having my Indy shop go over the whole car. They think it might be the fuel pumps since my spark plugs were just replaced.

[njdangelo]

Originally Posted by b58boi

Yes rough idle only present right after fill up. Once I drive for a good 5 minutes and I come to a stop there is no rough idle anymore. Very frustrating…having my Indy shop go over the whole car. They think it might be the fuel pumps since my spark plugs were just replaced.

Interesting, sorry you're still having issues. Hopefully your Indy mechanic can figure it out

[bimmer456]

Seems to do it a little if switching fuel brands. Maybe there is some lower octane fuel stuck in the hose initially and the ecu adjusting timing to accommodate.

[b58boi]

Originally Posted by bimmer456

Seems to do it a little if switching fuel brands. Maybe there is some lower octane fuel stuck in the hose initially and the ecu adjusting timing to accommodate.

Initially when it happened to me it was every time I switched fuel brands. Now it happens every single time I fuel up and I tried using the same station 3 times in a row and still does it. Then I tried every top tier gas brand and they all do it.

[CrimsonMoonLight72]

Originally Posted by njdangelo

I think letting the tank get too empty may actually effect it more but who knows. Glad you got it sorted. You should be able to replace it in about 3 minutes. easy as pie, just don't snap a hose or connector lol. They are plastic and not flexible.

Man I am concerned about breaking something.....I know those two vacuum hoses come off by squeezing them off. Then the other one comes off by prying a tab and then the valve itself I think pulls off of the silencer. Idk I may just have my mechanic do it.

[CrimsonMoonLight72]

Originally Posted by b58boi

Initially when it happened to me it was every time I switched fuel brands. Now it happens every single time I fuel up and I tried using the same station 3 times in a row and still does it. Then I tried every top tier gas brand and they all do it.

If you replaced the breather valve hopefully it’s on fully.....? But you should of gotten a code saying tank ventilation. I was very hesitant to order the new tank breather valve until I actually saw the tank ventilation code and finally I did see it.i cleared it through BM3. So if you got NO codes that is odd.....it could be something else.

[b58boi]

Originally Posted by CrimsonMoonLight72

Man I am concerned about breaking something.....I know those two vacuum hoses come off by squeezing them off. Then the other one comes off by prying a tab and then the valve itself I think pulls off of the silencer. Idk I may just have my mechanic do it.

I had my shop do it and not even joking it took them 2 minutes. Hopefully if you have a good relationship they'll just replace it for you no cost.

[b58boi]

Originally Posted by CrimsonMoonLight72

If you replaced the breather valve hopefully it’s on fully.....? But you should of gotten a code saying tank ventilation. I was very hesitant to order the new tank breather valve until I actually saw the tank ventilation code and finally I did see it.i cleared it through BM3. So if you got NO codes that is odd.....it could be something else.

Seeing everyone having the same symptoms I just went ahead and replaced it. It is odd that there are no codes but there is no way the car should run rough like that. The car is back at the shop and they're doing a full diagnosis as to what it could be. They're scanner is way more intricate than what I have so maybe they can see something I can't. They said if they don't see anything with the scan they might just reprogram the car and see if it helps. I simply don't want to drive the car and have something catastrophic happen leaving me stranded.

[hybrid90]

I had this same problem last year but luckily I'm still under CPO Warranty, so they replaced the Tank Ventilation Valve and I have had no problems since then. Here is the link to the thread I posted detailing the problem and solution if you're interested. Hope this helps:

https://f30.bimmerpost.com/forums/sh....php?t=1792891

[b58boi]

Originally Posted by hybrid90

I had this same problem last year but luckily I'm still under CPO Warranty, so they replaced the Tank Ventilation Valve and I have had no problems since then. Here is the link to the thread I posted detailing the problem and solution if you're interested. Hope this helps:

https://f30.bimmerpost.com/forums/sh....php?t=1792891

Do you happen to have the part number for it? I looked up “tank ventilation valve” and it was giving me the fuel tank breather valve/purge valve. Is it the same part? I had that part replaced and am still having the same issues so quite lost. Also no CEL or stored codes so really can’t figure out what’s wrong.

[hybrid90]

Originally Posted by b58boi

Do you happen to have the part number for it? I looked up “tank ventilation valve” and it was giving me the fuel tank breather valve/purge valve. Is it the same part? I had that part replaced and am still having the same issues so quite lost. Also no CEL or stored codes so really can’t figure out what’s wrong.

This is a pic from the service report. Looks like they are calling it a Tank Breather.

[b58boi]

Originally Posted by hybrid90

This is a pic from the service report. Looks like they are calling it a Tank Breather.

Darn… I was hoping it was a different part. I replaced this already and still have the same issues. Btw, how long did it take for the CEL to pop up after you started noticing the issue? I see you mentioned it was a couple months apart.