Hello everyone,

I have an 88 951 with:
3 inch Lindsey racing pipe
Billet Fuel pressure regulator
Wider Throttle body
Autothority Racing Mass Air Flow sensor
Boost Enhancer
Autothority stage 2 chips

About a month ago, I was driving and the nice woosh sound that i would get when I would shift from the turbo turned into a fluttering sound when I would shift. I was told by my Porsche mechanic that it was a bad baffle in the Lindsey racing pipe. He also replaced a few vacuum lines in the car and the car really moves now but still makes the fluttering sound because I have the race pipe still on. The problem is that I can floor the car in first gear and the car will pull all the way up to 6K rpm with no problems, I will then shift as fast as possible and then floor it in second and the car will pull crazy hard all the way to about 4K rpm and then the car will take about 2 seconds to get to 6K rpm. If I am just driving around town in second and floor it, the car will pull all the way to 6K rpm with no problems. It only has this issue when doing a straight line push as hard as possible. If i shift slow to second and then floor it, the car is fine. Its almost as if the car is sitting at that rpm and just slowly pulls to 6K rpm when it used to spin the tires and race to 6K rpm from 4K rpm.

I am not sure if the blow off valve is bad and the air is not escaping the turbo all the way before I gun it again when I shift real fast or if it is a vacuum line issue. If you could provide any help, I would really appreciate it. Thanks so much for your help.

 

The fluttering sound is probably a blown diverter valve. Are you still using the stock valve, or aftermarket? If stock, the diaphragm is probably torn.

 

Hi Porsche Doc,
I have had the BOV valve replaced and the vacuum lines replaced as well and the fluttering is still there. They were replaced with stock parts. Could it be a bad baffle in the exhaust or maybe the new stock BOV valve may be bad? I'm just worried that i may be damaging the car every time i take it out. Thanks for your help.

 

Sounds like you need to do some more diagnosing. Could be leaks in additional vacuum lines, wastegate diaphragm blown, collapsing downpipe or crossover, leaking intake or exhaust gaskets, bad/leaking injectors or fuel pressure regulator, Bad TPS (I would definitely check this out). You just have to get in there and start checking things out.

 

You were right!! I started to replace and pull out all the vacuum lines and would drive and it still had the same problem in second gear. I then went on to the pressure regulator and that had no effect. When i replace the fuel injectors, the car is now perfect. No hesitation at all any more. It just goes. I still am having the fluttering sound but the hesitation is now gone. Im going to check the waste-gate when i get some time this weekend and see if that is going or not. Thanks for your help. I thought i would never be able to figure out that hesitation problem. Ill let you know what goes on with the waste gate this weekend.

 

Hi Everyone, i checked out the waste-gate and noticed that it was fine. I am starting to think that the bypass valve is bad on my car. I know that it was replaced with am OEM one not too long ago, but i don't believe that it can handle the boost. I was going to upload a video of my car making the fluttering sound, but it is now at my mechanics. I have put a video below of the exact same sound that my car is making after i let off the gas. This video is not mine, but it does the same thing as mine. If everyone on here believes that it is the bypass valve that is shot on my car, what type do you recommend to replace the OEM one with? I saw on Lindsey racing that they had an adjustable one for $150, but i dont want to order the wrong one. Also, if it is the bypass valve that has been bad on this car, how much damage has been done to the turbo/ motor? It has been doing this for a few weeks and i have been pushing it hard a couple of times to figure out the 2nd gear hesitation issue. Thanks so much for all your help on this. I really appreciate it.

http://www.youtube.com/watch?v=MkkA-vfGWg0

Sorry for the crude video, but its the same sound as mine. Thanks again.

 

Just remove the vacuum line on top of the valve and suck into the nipple on the valve itself. If you can suck through the valve, then it is bad. If it holds vacuum, then it is good.

 

Hi Porsche Doc,
I apologize that i have not been on here for a while. My car was broken in to and i havent had the chance to do any other work on it. While i was waiting for the new window, i ordered a new aftermarket BOV. I put this on the car over the weekend and the fluttering is now gone. Thanks for all your help on this issue. I really appreciate it. have a great day.