My NB2 idles at 37-38kpa @ 900rpm (14.5 AFR, 17 degrees timing) and during hard deceleration pulls a vacuum of 21kpa.

Do these numbers look a little on the high side? I'm thinking the idle vacuum should be more like 29-32kpa and the decel vacuum more like 12-15kpa.

 

Numbers look high to me.

 

High. Should be 28-32 at idle and 12-16 at full decel in gear.

 

Suspecting a vacuum leak I re-torqued the upper intake manifold & throttle body bolts. Tightened up the boost hose to throttle body inlet. RTV'd my EGR blanking plates (threw away the old gaskets). Checked the vacuum lines to EFR recirc valve and to ECU.

Now idling at 34kpa and decel is 17kpa. Good enough?

 

That's where I am and my car runs great, nothing to worry about IMO

 

Not a vac leak situation. The car requires too much air to idle at the target speed. The car does not pull sufficient vac during decel.

 

Thanks guys. Didn't see these replies before my most recent post.

Yep it's running nice enough!

 

Thanks Ted. If you're suggesting the engine is worn/wearing out that wouldn't be unreasonable. It's a 110k mile totally stock motor that's been abused by an EFR most of this year. Still has 185psi compression across the four cylinders though.

Guess I'd better finish my forged motor build.

 

I have seen several different things that can lead to this, for example running 90 degrees of injection timing on a car that has been converted to sequential. Edit: this can cause high idle vac, does nothing to decel. Decel is related to the air pump.

But yes, a less than healthy motor qualifies as well.