MBC installed.. Some WEIRD problems
 

Ok well I installed a MBC, i have it running at about 10-12 psi. Now everything worked last night.. So now this morning i go to come to work here, and the whole car shudders when the turbo kicks in. There is NO power. i watch the boost gauge and it goes WILD. it goes from -20 to 15 to -20 to 15 so rapidly the gauge shakes too.!!!. and peaks sometimes at 25. then it feels like the car shuts off, and then kicks back on about 1 second later. Then my engine light starts flashing. So im not driving it like that, anyone have any idea? It runs fine at idle, and below where the turbo spools, but as soon as the turbo hits 1psi it goes wild!!!

You are going to blow your shit up.

What year is your car? Sounds like your have a dbw car and the boost controller isn't working anymore or the line popped off causing the turbo to over boost, then the ecu kicks in by shutting the throttle body and doing everything it can to reduce power.

Pull the MBC out and put the N75 back in.

:(... ill run the CEL codes i got and post them. i havent driven it like that.. for long.. maybe 1 mile to work. but i didnt let it spool that much.. explain to me 1 sec. the n75 valve.. ive seen diagrams where its all togeather bypassed, and ive seen t-fittings on it too. maybe ive done it wrong? im new to audi's and turbo cars. everything ive ever owned has had a chevy v8 in it. :P

Well lets start off with how you installed it and did you remove the N75 completely or did you just remove the 2 hoses and looped a hose from one of the open nipples to the other?

no here is what i did.. i had one end going directly into the wastegate and the other end going directly into the turbo. i bypassed the n75 completly.. but i left it plugged in.

That is fine as long as you pulled the N75 out of the turbo inlet hose, if you didn't then you have unmetered air being sucked into the turbo hose.

ok . well i checked everything over.. my bad. i had a vac line from the mbc resting against something hot and there was a hole in the line.. DOH.. ok well now another problem.. i hooked everything back up, but with a t-line going to the n75 . and to the mbc. i have stock boost and cant ajust. and i have a TON of misfires still.. i get these codes. p0302 , p0301 , p0300

the mbc is hooked up exactly to the 2nd photo on this page.. https://www.audiforums.com/forum/diy-do-yourself-55/how-hook-up-mbc-68777/

This way?

http://ctny.audiworld.com/mark/s4/mi...c_parallel.jpg

That is in parallel and is done to reduce boost spikes or lower boost, you can not increase the boost because all you are doing is adding a 2nd path to the WG. If you want to increase boost put it back the way you had it or MBC inline between the N75 and the wg actuator.

yeah thats the exact way i hooked it up......

.. ugh ok well.. what do i do about all these misfiring codes?

Fix the MBC first and then clear the codes, clearing the codes will reset the fuel trim.