2001 Saab 93 2.0LPT funny sound under acceleration

Wheelio

Hopping someone on here could point me in the right direction to cure a funny sound my 93 has developed.
I recently had an orange eml light on and after getting codes read and changing turbo bypass valve light has gone, no error codes but the car makes strage sound under acceleration between 2900 - 3500 RPM and goes again after this.
Its sounds like air could be escaping somewhere and causing something to vibrate, very hard sound to describe. Mechanic looked around and couldnt see any obvious problems.
Anyone any experiance of this.

thanks.

Anan1

Split/loose hose?

Wheelio

Thanks Anan1, that is the most likely but neither myself or a mechanis could find a split or loose one and replaced a few before I replaced the bypass valve but will have another look.
Its just funny noise only came after replacing this valve.

Anan1

And you're sure the new valve isn't damaged and is installed correctly - right way around and all that?

Wheelio

Yea, pretty sure it is on the right way, it is a spurious part I've used though but it came recomended by a good saab indy who has used in the past

Anan1

Wheelio wrote: »

Yea, pretty sure it is on the right way, it is a spurious part I've used though but it came recomended by a good saab indy who has used in the past

Could you try putting the old valve back on, see if the noise is still there?

Wheelio

Unfortunately the old part has long since been dumped..
If I accelerate through the rev range slower the sound is not there, its just when I put the foot down

Make sure the new bypass valve is connected like this but it is most likely a fault/trait with the new valve:

http://www.google.co.uk/imgres?imgurl=http://farm5.static.flickr.com/4117/4875226453_04c5f402e1_o.jpg&imgrefurl=http://saabworld.net/f9/new-vacuum-lines-368/&h=678&w=699&sz=94&tbnid=Pf-GsJ_qH9s6fM:&tbnh=86&tbnw=89&zoom=1&usg=__dG-NvMDPODreUv93CRQQmzlp0RI=&docid=dilCqpBM4K5FYM&sa=X&ei=l2cCUoCXA4WB4ATnvIGABA&ved=0CDMQ9QEwAg&dur=647

The valve is used to recirculate the extra charge back on front front of the turbo when throttle is suddenly closed following a hard acceleration. It operates using pressure difference between inlet manifold and charge duct between the turbo and the throttle body. To reduce turbo howl the valve is also constantly kept slightly open under normal driving conditions. When the boost pressure is high in the intake duct, yours probably passes some air past the seal which vibrates and makes the extra noise. If the performance feels normal I'd just leave it tbh.

Wheelio

Thanks Samih, that kinda makes sense and it doesn't effect performance, just sounds different than before, as you said could be the trade off to getting cheaper spurious part.

Wheelio

Problem solved, found a hose not connected properly up by the firewall.