johnny

thanks for your reply Greydog, the battery was registered and never been an issue. the issue seems to be the computer failing to get the idle speed right, even after driving it over a hundred miles. what is odd is that if i gun it on starting the turbos do kick in and no warning light comes on but after maybe ten seconds it does come on every time. which indicates the turbos are good. i dont have a scan tool to read the codes but am looking into purchasing one, tho there are so many its hard to know which to buy, and not knowing if a scan tool can set the idle what sense is there in buying one till i know more. the car idled very rough at first three weeks back after reconnecting the battery but its much smoother now, and idles better than ever once the reduced power warning comes on, it always comes on with a slight surge in rpm. car runs great but for no turbo power due to limp mode and SES light stays on all the time. these bmw's are frustrating creatures to be sure, but great fun when right.

2008 335i changed valve cover gasket and plugs with battery disconnected for several days, after repairs made car ran poor, shifted hard, steering hard, idle erratic tripping reduced power and SES light ... after 2 weeks driving steering and shifting better but reduced power and SES still come on so no turbo power, car was fine before disconnecting battery. both DIY's for valve cover gasket replace indicated the battery disconnect with no warning about computer control module losing settings, miss the performance, no fun without turbo power, please help