Here's a video where if you listen closely you can hear what I'm going to describe below.
http://www.youtube.com/watch?v=HkzIM...ature=youtu.be

I'd like to pool the collective knowledge of everyone on here regarding a problem I'm having. My car is stock aside from an Alta CAI + Hose I installed around Christmas. When accelerating (not WOT) from around 3800rpm+ and say 20-50% throttle, I get a choppy stuttering and (perhaps because I can hear more due to my airbox) a quick "swish swish swish swish" along with that stutter.

Initial thoughts were it might be the supercharger belt slipping or something, so that was replaced and no difference. Because at lower speeds it sounds like a little "fluttering" of air, we then figured we would try the BPV (bypass valve) since that spring might be worn out and the valve might be flopping around or something. After replacing the BPV (the new one had noticeably more tension than the old), I'd almost venture to say the swishing got worse and the amount that you can feel it seems to have been exacerbated.

What do you guys think? We're going to look at the MAP (I think that's it) sensors next. What would cause this at say 20-50% throttle but not WOT?

Car is a 2006 R53 with 58k miles for those wondering. We also checked and car has the most updated software.

 

does your car have a tune on it? Mine was doing this because I had a bad TMAP sensor and it was reading 200+ degrees even when cold. No CEL's because of it either. Mine still is chugging between 2-3500 only on partial throttle but running fine at WOT.

 

No tune and getting no codes. I think that's one of the reasons the BPV was suspected- the no code thing. Was yours sounding like mine, and you're still having this problem?

 

ya but mine is a problem with my tune now. I did by a BP valve but was told it was in good working order. If you wanna save a little from buying a new on from Detroit Tuned I have a brand new one from them I just got (will even include my reciept from last week I will take some money off it

 

however, I think it is the 04 and earlier that had the spring issue in the bypass valve. I bet you have a bad TMAP sensor

 

Some free checks for you:

1. BPV, zip tie it shut, if there's a change that's it, but usually a BPV will give you issues more on top of the rpm.

2. T-MAP sensor, usually lower rpm issues is the sensor off the intake, but, usually the car won't want to idle either, (SOMETIMES this works), pull it out, swish the sensor end itself in some rubbing alcohol to rinse the oil residue off of it, won't really fix it but if there is a slight or temporary change, that would be an indicator. As I said doesn't always work, but it's worth a shot considering it's free & takes about 5 min. to do.

 

Maybe not the TMAP then? It idles fine and the noticeable issue is at higher RPMs. We replaced the BPV so that must not be the problem. If it primarily happens above 4k rpms, would max boost have been achieved and could it therefore be a vacuum issue or leak? Then again, it seems fine when wide open. Just thinking out loud and I am clearly not knowledgeable on this.

 

Someone has to have seen this before! Help please :-)

 

Sorry to bump but taking the car back to the shop Wednesday and I REALLY need some ideas on this one.

 

It would help to have a better video in which you are making clean accelerations at steady throttle without traffic around.

- Mark

 

Could this be caused by a dirty fuel filter? How about fuel pump?