Well, I just now got home after some hard runs, like redlining it a couple times. On my way back, the idle started messing around at traffic lights and droping almost to the point of shutting off. It actually did while i was in a drive through line and all i did was take my foot off the clutch for like less than a second. Also, ive been noticing my brake would drop the idle a couple hundred rpm's. What do I do?!

 

Vacuum leak maybe? Not too sure but sounds like it to me.

 

Your BAC valve sounds messed. It controls the amount of air entering the intake to compensate the engine for the loads that other operations of the car create.

 

yeah...sounds like theres a leak somewhere....most likely a vacuum or intake leak......

 

Well, I just installed a new apexi intake, what should i do if its the BAC valve?

 

i have the exact same problem right now, im suspecting the variable resistor, mine is broken...

 

Yea, I dont want to sound like a newbie, but ive never had to deal with the variable resistor, can it just be replaced?

 

General rule of thumb...never tough the variable resistor. It's set perfectly at the factory. I've never heard of anyone's variable resistor breaking. Unless you took a sledgehammer to it or something. I would recommend checking for leaks. Sounds like maybe a hose cracked or something.

 

yeah....sounds like it to me....if ur bac is cleaned...then thats one less thing that could be broken/dirty

 

It sucks, but ive never actually had a rock solid idle in the first place. If I have a leak in my vacuum hose and I fix it, is there a possibility my problems will be solved?

 

after driving a while my idle drops to about 500 rpm and the only thing i can think of is to get an air-fuel controller

 

Yes, if that was the main problem.

 

I actually had a leading spark plug wire slip off while driving.

I thought the engine had taken one huge ****.

Imagine that, a **** taking a ****.

 

which variable resistors are you talking about? TPS? idle mixture?

 

the idle mixture, the one down by the pressure sensor that has a big L and R to adjust rischness at idle. like gingenhagen said, dont touch it. the reason i know mine is broken is because it is only supposed to make like 1 1/2 complete turns and mine just continuously turns, it is stuck on lean and i cant richen the mixture to get it to idle.

 

I have this exact same problem. After a hard run like redlining thru 1st and 2nd my idle will drop down to where it looks like it should die and the shifter shakes. I know that my engine isnt weak I just had a compression test done and it was around 105 on each rotor.

 

where can you get a BAC filter?

Lordco? what part number would it be?

just to clarify, the BAC is a little vacuum valve that exposes when you take off the stock air box right?

 

Yea thats it, is there any good FAQ in the archive for revoming and cleaning the BAC for an S5? I was searching through the net and I found one for first gens, is it the same process?

 

check spark, that what mine was doing when a plug wire came off and what a my buddy's did sorta whaen one set of coils went up