if you have half a brain, DO NOT do this high-school-quality "mod" to your expensive and finicky car.
i am running a JB3 2.0 in my car, plus intakes. that's it. my exhaust flap was noticeably loud and shitty-sounding at cold start, and i had to wait 3+ minutes after start-up to drive away as there was a nasty-sounding metallic rattle until the flap opened. have even had a few people ask me what it was. so, having done this mod to my '07 with seemingly no problems (we'll get into that later), i got sick of this horrible sound on my beautiful car, and unplugged it.
less than 2 days later (keep in mind my car only has 55k km on it), i am driving along when i get the dreaded "limp mode" light. i quickly pulled over, turned the car off, sat for 5 minutes, and started it again. waited 5 more minutes, drove away, and got to my destination without further incident. it happened once more a few days later. same exact sequence of events.
THEN, i'm driving home a few days ago, and the light comes on again. that's 3 times within a week that my limp mode light has come on, after never coming on once before in EITHER of my cars, and all within the week AFTER unplugging my exhaust flap, but this hadn't dawned on me yet. i do the usual pull over, turn car off, wait 5, start up, wait 5, drive away. literally less than 20 minutes later, it happens again...this is the first time it happened more than once in a day, but THIS time...the Check Engine Light (CEL) came on too. i pulled over and started freaking out, when it dawned on me...in a flash, i was out of the car, digging around behind my tail-light at the side of the road at 2am, trying to plug the damn thing back in.
i plugged it back in, started the car, waited 5 minutes, and drove away. got home without any more limp-mode lights, but the CEL was still on so i'm fuming. start the car the next morning to go to work, CEL still on but not a single limp-mode light during my 40+ minute drive. mid-day, go out to my car to go get lunch, start the car...and much to my delight, the CEL turned off all by itself! i did a little dance and patted myself on the back, and neither the CEL nor the limp-mode warning has presented itself ONCE since then.
i'm not exactly sure why this all happened. i had the flap unplugged in my last car, an '07, with the same mods done to the car, as well as a resonator delete on that one. the CEL came on in that car right before i traded it in, but i never thought to try plugging the flap back in as a fix. but it sure as hell worked on my '08!
i don't know if it was a case of my JB3 chip interfering or miscommunicating with something, as i've heard guys with stock cars running this "mod" for years without any problems, but i will NEVER even consider unplugging that thing ever again after my experience, no matter how shitty the metallic rattle may sound at start-up.
take my story as you will. but keep in mind that it's not the smartest idea to go around unplugging sensors on a electronic masterpiece like a BMW. that flap was put there for a reason and unplugging it, as you can see from my example, could have dire consequences.
'08 monaco blue E90 335i 6MT. sport pkg. premium pkg. black leatherette. brushed aluminum trim. M-Tech shift knob/boot. M3 mats. matte black kidneys. carbon performance trunk spoiler. blacklines. MTEC angel eyes. JB4. aFe stage 2 intake. custom downpipe-back stainless exhaust with 4" tips. mechunik plate mount. 19x9/19x10 +24 style 95's with 10mm BMS spacers in the rear.
Last edited by 335alive; 06-25-2012 at 09:54 PM.