Having a little 'increased emissions / close gas cap' issue

[///Master]

Soo I seem to be getting a 'close gas cap' light when driving, which is later followed by an 'increased emissions' light after time / miles. I got a new gas cap & replaced the DTML pump. I am still getting 'close gas cap' message.. argh

My scanner reads a p0442 code which says 'small evap leak detected.'
Do you guys think it may be the fuel breather valve? ( I did get bearings & spark plugs done recently.. thought id throw that in there )

M3's at 36k miles - pre-LCI

Any advice would greatly be appreciated! (my smoke test didnt show any obvious leaks)

[EJT86]

The fuel breather doesn’t throw a code and when it goes its doesn’t leak it just stops sending fuel vapor to be used. Also you’d have symptoms like a bouncy idle or stalling. Did you clear the code when you put in the new cap?

[///Master]

Originally Posted by EJT86

The fuel breather doesn’t throw a code and when it goes its doesn’t leak it just stops sending fuel vapor to be used. Also you’d have symptoms like a bouncy idle or stalling. Did you clear the code when you put in the new cap?

I cleared the code Saturday with my Autel Scanner and within 5 miles of driving 'close gas cap' illuminated again.. I'll have to drive the car to work today / tomorrow and see if i still get the 'increased emissions' after. And i don't have a bouncing idle.. What a headache

[EJT86]

Originally Posted by ///Master

I cleared the code Saturday with my Autel Scanner and within 5 miles of driving 'close gas cap' illuminated again.. I'll have to drive the car to work today / tomorrow and see if i still get the 'increased emissions' after. And i don't have a bouncing idle.. What a headache

i doubt its the fuel breather then i dont have any other advise but i feel like this is something that has been discussed on the forum before idk

[Jobe.]

You mentioned clearing the code Saturday then driving the vehicle 5 miles.

Did the vehicle sit overnight and you drove the vehicle at a later date?

The fuel level has to be at a specific level and ambient temperature has to be within a certain specification before the vehicle will run an evap leak test.

If you drove right away that would lead to another issue causing a leak code not an actual leak.

[///Master]

I haven't been driving the car much at all due to the weather.. But I drove the vehicle home which is about 15-17 miles after clearing the code, then parked it in the garage & havent driven since. (Gas cap open illuminated within 5 minutes of driving). Looks like I should keep driving to get the evap sys. to run then?

Originally Posted by Jobe.

You mentioned clearing the code Saturday then driving the vehicle 5 miles.

Did the vehicle sit overnight and you drove the vehicle at a later date?

The fuel level has to be at a specific level and ambient temperature has to be within a certain specification before the vehicle will run an evap leak test.

If you drove right away that would lead to another issue causing a leak code not an actual leak.

[Shaan]

Originally Posted by ///Master

Soo I seem to be getting a 'close gas cap' light when driving, which is later followed by an 'increased emissions' light after time / miles. I got a new gas cap & replaced the DTML pump. I am still getting 'close gas cap' message.. argh

My scanner reads a p0442 code which says 'small evap leak detected.'
Do you guys think it may be the fuel breather valve? ( I did get bearings & spark plugs done recently.. thought id throw that in there )

M3's at 36k miles - pre-LCI

Any advice would greatly be appreciated! (my smoke test didnt show any obvious leaks)

ive been having the same problem. changed the DTML pump but that didnt help. ill find out what exact part my mechanic changed but i believe it was a fuel pressure sensor. Still have a check engine light due to a bad 02 sensor but the gas cap message went away.

[///Master]

Originally Posted by Shaan

ive been having the same problem. changed the DTML pump but that didnt help. ill find out what exact part my mechanic changed but i believe it was a fuel pressure sensor. Still have a check engine light due to a bad 02 sensor but the gas cap message went away.

Yeah let me know any help would be greatly appreciated at this point 👌

[Patrón]

the gas cap is pretty cheap, have you tried replacing it?

[///Master]

First thing I did was get a new gas cap

Originally Posted by Patrón

the gas cap is pretty cheap, have you tried replacing it?

[Patrón]

Originally Posted by ///Master

First thing I did was get a new gas cap

damn it. then it's either your charcoal cannister or the gas tank evap under the manifold towards the firewall. it's not that expensive and should take less than an hour.

just read your first post, sorry i recommended the gas cap. for some reason our cars had problems with the tank evap part. it's really easy to change.

[///Master]

thanks, Appreciate your input. I was wondering if my charcoal canister is ok.. I checked the fittings / smoke tested, seemed fine. Are you talking about the Fuel Tank Breather Valve or the Fuel Pressure Sensor?

Originally Posted by Patrón

damn it. then it's either your charcoal cannister or the gas tank evap under the manifold towards the firewall. it's not that expensive and should take less than an hour.

[Patrón]

Originally Posted by ///Master

thanks, Appreciate your input. Are you talking about the Fuel Tank Breather Valve or the Fuel Pressure Sensor? or something else?

fuel tank breather valve. but now that you mention the fuel pressure sensor, i would change that if the breather valve doesn't fix it.


i use to have the symptoms of the breather valve problem where my tank fill up would stop during the fill process. i would run race gas every once in a while and that would fix the issue. OR i would put a bottle of techron once or every other month.

[EJT86]

Originally Posted by Patrón

fuel tank breather valve. but now that you mention the fuel pressure sensor, i would change that if the breather valve doesn't fix it.


i use to have the symptoms of the breather valve problem where my tank fill up would stop during the fill process. i would run race gas every once in a while and that would fix the issue. OR i would put a bottle of techron once or every other month.

a flooded vapor canister is what makes the pump stop during fill up and doesnt throw a code like whats happening to the OP. the breather valve also does not throw a code and he has no symptoms that go along with either a failed/failing vapor can or breather valve

[Patrón]

Originally Posted by EJT86

a flooded vapor canister is what makes the pump stop during fill up and doesnt throw a code like whats happening to the OP. the breather valve also does not throw a code and he has no symptoms that go along with either a failed/failing vapor can or breather valve

is it possible to clean the cannister?

[EJT86]

Originally Posted by Patrón

is it possible to clean the cannister?

sucks but no...its charcoal but spongy inside and doesnt come apart i believe BWD makes an aftermarket one or do what i did and buy a used one on here just gotta find a wrecked M3

[Shaan]

Originally Posted by ///Master

Yeah let me know any help would be greatly appreciated at this point 👌

Confirmed. Fuel pressure sensor. Hope that works for you