Loss of idle vacuum...

[mincemeat]

My Legacy usually had about -0.7 bar of vacuum when idling, but about two days ago it started to decrease... it's only about -0.4 bar today. The idling speed seems to be unchanged.

What could be causing this problem? Any hints on how to diagnose this would be great... TIA

[Moppie]

Well since the vacum level is RPM dependant I would start by checking the guage, and the vacum lines that its conected to.
Does it still show your reaching MAX boost?
(I assume its a GT or RS)

[mincemeat]

That's the first thing I've checked - seems to be nothing wrong there. Top boost is still shown correctly.

The idle RPM is normal and constant - I wouldn't know something is wrong if not for the boost gauge.

I've taken it to the mechanic and see what he says...

[Moppie]

Originally posted by mincemeat

I've taken it to the mechanic and see what he says...

I would be most interested to find out what he says.
I wonder if its a turbo spinning at idle?

[mincemeat]

It turned out to be a fracture on one of the hoses that the gauge was teed off...

Come to think of it, even with such a fracture the top boost level will still show up correctly simply because of the amount of air flow in-boost.

Oops...

On a semi-related note while the said mechanic was sorting out my fouled plugs I ask him for a compression... the highest was ~140psi while the lowest was ~125psi.

They look somewhat uneven but is it an acceptable amount of variance?

Thanks

[Moppie]

Originally posted by mincemeat
It turned out to be a fracture on one of the hoses that the gauge was teed off...

Thats not a bad compression variance, I wouldn't worry about it unless your looking at really cranking up the boost.
However it does show that the car is getting old, and the engine is getting worn. But as long as its not burning large quantities of oil I wouldn't worry about it.

I assume its an import?

[mincemeat]

Yeah it's a Jap import although I'm like the 3rd NZ owner anyway. Odometer at 220+. I don't think it's been wound back, even if so it can't be that much...

Yes I do plan to crank up the boost in a big way, aiming for ~17psi. Already got a VF23 bolted on, so why stop?

[Moppie]

Originally posted by mincemeat
Yeah it's a Jap import although I'm like the 3rd NZ owner anyway. Odometer at 220+. I don't think it's been wound back, even if so it can't be that much...

Yes I do plan to crank up the boost in a big way, aiming for ~17psi. Already got a VF23 bolted on, so why stop?

hehehehehehehehe.

With 220,000 on it I wouldnt expect it to last to long running 17psi.
It will go like stink, then just go POP!

But then the engines are pretty common and easy to get so you can either rebuild your one, or just slap in another one and go hard again.

[olds88]

acculy even with high milage those boxermotors are dam near bullet proof they only have a small problem with piston slap