staplebus

Hi to all. i recent installed a vitesse maf, 72lb injectors and 3in exhaust. before all of this i had close to 19in of vacuum at idle. now its around 15in but at start up maybe 10in and jumps around slightly from there. also its running lean at idle, flucuation up to 17 when it shows low vacuum. Ive tripple check all of my install points and vacuum hoses, injectors and everything. the only thinng i can think of is not related to the install...

I hear a hissing noise from the isv and if i pinch the hose that connects it to the intake pipe the hissing stops. also if i move the throttle plate just enough to make it click but not enought to change the rpm on the tach, my vacuum jumps right up to 19 and my idle smoothes out, AFR goes back to 14/15. I just cleaned th isv and nothing. can the isv leak internally?? is it supposed to hiss?
thanks so much-Kyle

staplebus

forgot to add i do have a 3 bar fpr before anyone asks.

Ski

Double check the vac lines, do an idle reset. The ISV is installed in the correct orientation?

Tom M'Guinn

I once did a smoke test on my intake system once, and the old ISV leaked quite a bit at the joints. Don't know how common it is, but I ended up getting a brand new one, which proved air tight.

staplebus

thanks for the input! isv has the arrow pointed to the manifold, i believe this is correct. all vacum lines are sealing. i can do an idle reset, but is this a common procedure after a maf install? also, that hissing noise has got me worried, and it stops when i pich the hose that hoes to it from the in take pipe. do these things hiss on your cars? im of to hawaii for a weekso ill have to check in later. ill try that reset when i get home. thanks again any more input

staplebus

im back and im planning on doing the idle reset tomorrow... but just to comfirm, does any one else's isv make a hissing noise at idle that stops when the hose from the intake to the isv is pinched off, thanks!

slee11

mine makes the same hissing noise during cold starts. I think that noise is just air bypassing the ISV.

cas951

I have the same issue. Lo vacuum when cold around 15 when warm. All vacuum have been checked and rechecked. No leaks. Eng has good compression.

Black51

Was this problem ever solved?