Rough idle in cold and outside temp sensor related

[TCACEK]

I have very rough idling when in extreme cold but only when in gear which makes me think it is transmission related. However my gas milage plummets from 18 city to around 13 in the extreme cold. Is there a relationship (sensor, feedback etc) between the outside air temp and fuel mixture/idle programming. I would if my gas/air ratio is changing because of faultly data given to the obc. just a thought. your thoughts appreciated.
04 325Xi, 74k

[JKRIT]

If you don't have the insulated, cold-weather CCV valve and tubes, they tend to get blocked with sludge in cold weather and cause idling problems, among others (like blowing up hoses). You could carefully pull off the CCV hose to the front of the valve cover and look in there for sludge, just as an indication. The hose is brittle, so don't yank on it or you will break it. Total conversion to cold weather set-up seems to run about $800 at the stealers.

Your Vanos seals are not functioning properly by this mileage, so you don't get the intended cam timing at idle (and other RPMs). With manual tranny, this means (among other things) difficulty launching without stalling; with auto tranny, you can get a rough idle. DIY Beisan vanos seals in about 4-5 hours and less than a hundred bucks, or pay more for a rebuilt Vanos unit.
'03 525i Sapphire Blu/Grey, SP, Nav
'02 325it Orient Blu./Grey, SP, Nav
'98 323is Arctic Sil./Blk, SP
'95 M3 Cosmos Blk./Blk

[dembooks]

and......


what's the air filter look like ?

gas filter ?

fuel pressure reading ?

what oil are you using ?

& how ofter (miles/months) does it get changed ?

[dembooks]

operation of the coolent thermostat ?

oprating temp of the engine ?

[tcek]

All you previously questioned is new/operational but oil was 10-30 and had 10k. Changed to bmw 0-30 and seems to run better. Still having rumble (shaking) at stop with car in gear. thinking it is something in auto tranny or at least in that area.

[dembooks]

.........well then, you need a Fault Code Readout
from your BMW dealer to stop any quess work
to determine what's up. Way too many variables and
possibilities for anyone on the internet to diagnose for you.

and i doubt any connection to the Automatic Transmission
at idle, if the car "seems' smooth at any mph ?