Originally Posted by lfpontes
I own a 335i E90 N54 auto here in Brazil.. It has AMS DP, K&N inbox, COBB, and AA BOV .
Everytime I change my current map with the cobb system, the car seems to be stuck in 2nd or 3rd gear for a while, and suddenly it drops to 1st after a few ft of driving and everything stays normal.
This only happens right after I switch the map, when I turn on the car. And only one time every time the map is switched.
Also, if I select Reverse before the car has dropped to 1st, there is a big CLUNK noise coming from the transmission.
Why does this happen? I cant seem to find any plausible answers on Google or any other source. Also, the car missfires a little bit in its first start in the morning.
I am not sure but it Seems like its a transmission problem. Does it ever happen when you are on stock map? Does it happen when the car is cold more importantly when the transmission is still cold and things go back to normal after you've driven the car for a while? if so then i guess the valve body/tcu has a problem, i think its best to check if the transmission has stored any faults. Again i might be wrong just asking for clarifications.