What is this on a GTV6 Engine

[Fylnn]

Does anyone know what this thing does in a 1983 GTV6 engine?  It seems to have 2 connections to the plenum chamber and one to the inlet trunk to draw in fresh air. 

Thanks in advance

[Al Campbell]

That's a vacuum regulating valve. Only used in Switzerland, Sweden & Australia for emission control. I think the idea is that on over run from high revs if there's too much vacuum in the inlet manifold  it causes poor emissions, so they open up a pipe to the inlet side of the throttle. Probably doesn't have a lot of effect on a 27 year old engine.

It's mentioned in the workshop manual on Craig's place, Group 4, fuel system, pages 78/1 and 79 :

http://www.users.on.net/~craigf/

I had a problem with idle on my car when it was fully warmed up where sometimes the revs would speed up and then hunt as the fuel injection couldn't work out wether it was idling or low throttle, eventually tracked it down to that valve. My car has shot rings and burns oil like so that valve I think is clogged. I  disconnected it pending rebuild or replacement motor (plugged the three holes of course).

AL.

[Fylnn]

Terrific thanks.  It sounds like something I can safely consign to the scrap bin and tidy up the pipework.  Thanks for the help.

[Al Campbell]

You may have to adjust the idle speed after you've removed it.

[Fylnn]

Yes true, but I am clearing the decks so to speak, for a Haltech installation so should all be taken care of.

[lombardi]

How do u adjust idle speed on gtv6,ie fuel injected.rgrds ciao

[Al Campbell]

Lomabrdi,

In the photo at the start of this topic, if you look at the pipe second from the left going into the plenum, there are 2 nuts. The one closest to the plenum is a lock nut (also holds the bracket for the vacuum valve), the other nut which the tube is attached to is the idle adjust.  Use a thin open ended spanner to loosen the lock nut then use another spanner to turn the outer nut. Turning it clockwise compresses a rubber doughnut restricting the air flow which slows the idle. Anti clockwise speeds up the idle. Set it when fully warmed up of course.

AL

[lombardi]

Thanks AL for your valued info,the engine is idling when warm at  just over 1100,i believe this is a bit high,have been told should be between 800-1000,is this correct.rgrds

[shane wescott]

had an issue a couple of times where the pipe third from the left comes off - GTV6 wont idle and stalls.

Took me 30 mins the first time to spot the pipe off, after that it is one of the first things I check :-)  Who said an old dog cant learn new tricks.

Interesting info on the idle adjustment  - thanks for that.

[Al Campbell]

I have my idle set for a bit over 1,100 as the auxiliary air valve doesn't work too well in the cold weather. When the air temperature is below 10 C and the car's dead cold my idle drops to 600 rpm for as few moments, which is as good as I can get it with my old wheezy motor. The problem with the idle hunting as the L-Jet gets confused doesn't happen until around 1,300 – 1,500 rpm. So in other words I set it as low as I can without the car stalling when it's very cold.

For a good practical guide to setting the idle etcetera, have a look at Greg Gordon's site. The idle part is buried in the middle but it's worth a look

http://www.hiperformancestore.com/Ljetronic.htm

AL.

[lombardi]

Awesome info,thanks

[wetprickles]

My car has shot rings and burns oil like so that valve I think is clogged. I  disconnected it pending rebuild or replacement motor (plugged the three holes of course).

AL.

Hi AL
Sorry to interupt but what noises do you remember your engine making with the shot rings?
You could reply on this thread, or here;
http://www.alfaclubvic.org.au/forum/index.php?topic=3480.0
Leon