Vacuum pipe?

[Lukey904]

So I've just bought a 172 that runs rough at idle , it has a k and n filter fitted , but just before the throttle there is a nipple for some sort ov vacuum hose that isn't connected/ is missing , could anyone help me as to where this should run too ??

 

[MRBILLYUK]

Sounds like someones removed the acoutsic valve down in the offside wheel arch . The vacuum pipe / nipple should have been blanked off . That'll be why your idle is rough , probably running high . Blank off the nipple and see if it makes any difference . 1*2's do run rough at idle anyway , and should be around 800rpm once warmed up .

 

[Lukey904]

Sounds like someones removed the acoutsic valve down in the offside wheel arch . The vacuum pipe / nipple should have been blanked off . That'll be why your idle is rough , probably running high . Blank off the nipple and see if it makes any difference . 1*2's do run rough at idle anyway , and should be around 800rpm once warmed up .

When you dip the clutch it feels like it might almost cut out , just bounces off a low idle for a second before idling rough again . I put new plugs in it and like I say I wasn't sure if it was meant to be connected to some form of throttle bypass or idle air control valve .

 

[banderson]

Let me know how the blanking off goes mate. Mine has had the acoustic valve removed too, and found that the pipe (mine had a pipe attached still) had a split in it and was leaking vacuum.
It has run rough for over a year and I've replaced several bits before finding this. I just can't test mine yet as the driveshaft has gone

 

[Lukey904]

Let me know how the blanking off goes mate. Mine has had the acoustic valve removed too, and found that the pipe (mine had a pipe attached still) had a split in it and was leaking vacuum.
It has run rough for over a year and I've replaced several bits before finding this. I just can't test mine yet as the driveshaft has gone

Yeah I'll let you know mate ! I bought the car off a pal at work and I'm a mechanic by trade so thought air leak straight away , I didn't know what the vac pipe should have been connected to but drawig air all the time can't be helping . Got a few other niggles I'll probably be asking for advice on aswel haha.

 

[banderson]

Yeah I am mechanic by trade too mate, but when it comes to my own car though I panic lol and I have to ask for advice. I just presumed that pipe was blocked off still so didn't give it a thought, till last week I was fiddling and heard it hissing under the battery lol looks like battery acid (or something) had dropped on the pipe and made it all crack up and fall apart.