Craigito

So my buddy has been borrowing my car for a few days while he gets the TB and other crap done on his A4. He agrees with the overboosing/surging issue so it's not my imagination

So last time I posted, the responses I got were perhaps a bad throttle position sensor (not sure where that is located or how to fix)...bad wastegate or N75. The MAF is fairly new. I don't think the turbo is bad because it puts down some serious boost (too much sometimes)

Again, to try to explain what the car does. Under constant throttle the car surges heavily and then you can hear what sounds like an airy sound as the car slows..then you can hear the turbos boosing again and then slows. All this is under constant throttle. It is especially apparent when going up a grade trying to hold your speed.

Sometimes the car surges so much the throttle completely closes suddenly without warning and car goes to idle with no throttle response (car is on...just idle). When this happens the EPC light goes on. This is lots of fun when your doing 75 on the freeway and have to turn the car off and on to get the throttle back.

I'm only trying to get it fixed to sell it. I don't want anyone test driving it in this condition. Hopefully it's a cheap fix.

Any other ways to check what it might be? I don't want to start buying parts to find out it's not the problem. I'll get some OBD codes pulled soon to help diagnose it but you guys have any other opinions?

Thanks.

@wesome

This is what I would do. First pressure test the entire system... Overboosting is usually related to the lines on the n75 to the wastegate
If the line is loose (or even cracked) you may end up overboosting which would explain the "airy sound"

I'm not sure what else it could be...

Craigito

Thanks...I'll have to STFA for how to pressure test.

Silver Streakin'

but, I've checked and replaced mine, but still have that odd overboost issue. some day, I'll put in the homemade MBC and set it to ~20.

Craigito

Oh...running a K04-GIAC setup...