Mk1 Vacum Leak

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Igor
Posts: 2184
Joined: Thu Feb 03, 2005 5:13 pm

Mk1 Vacum Leak

Post by Igor »

I seem to what sounds like a vacum hose leak coming from somewhere, You can hear a definte hissing coming from somewhere. I think i have defined it down to what i think is the MAP sensor? Picture below thing with 2 pipes going to it, with brown and green coloured plastic. It seems to be affecting the tickover as i if i squeeze either of the 2 pipes going to it the hissing stops and the engine cuts out. I also reckon the TVIS is not giving its full kick that it should?

Image

Can anyone help with this?

Should it be hissing?, Is this something common? I can't seem to find any obvious leaks?

Thanks

Igor
PW@Woodsport
Posts: 7642
Joined: Tue Dec 14, 2004 6:40 pm
Location: durham
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Re: Mk1 Vacum Leak

Post by PW@Woodsport »

thats your idle up vsv,it comes on when you have an electrical load applied ie heaters on,heated rear screen on,brake lights operated and loads more....it allows a small air leak into the throttle body to raise rpm by a few hundred.If you are pinching the pipes and its cutting out then the idle speed screw isnt wound out far enough on top of the throttle body....also if you can hear hissing then the vsv is drawing air from atmosphere.Theres two pipes coming from the vsv,one should go to the left hand side union on top of the throttle body and the other should go to a fitting on the inlet tubing so that its sucking filtered air,it makes no difference which pipe goes where,they are swappable.

Get the engine to full temp,switch off all electrical loads (if necessary remove the electrical plug from the vsv in your picture) and adjust the idle on top of the throttle....now reconnect the vsv and switch your heaters on,the idle should rise slightly.

All of the above is presuming your ignition timing and idle mixture is set up correctly and there are no other problems,hope some of that helps.
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Igor
Posts: 2184
Joined: Thu Feb 03, 2005 5:13 pm

Re: Mk1 Vacum Leak

Post by Igor »

Thanks i shall give that a try.

Cheers

Igor
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