ISV doesn't fully close

mallard ducks · 05-21-2009, 07:41 AM

Hi - is anyone familiar with ISVs?

I'm trying to get to the bottom of a high idle condition and I'm wondering if the ISV on my 944S is operating correctly.

It is a 2-pin: resistance across the pins is in spec; it buzzes with the ignition on; and when I test it with a 9v battery it opens and shuts when the power is put on/taken off...

So what I'm wondering is: in the shut position is the valve supposed to be fully shut? Or is it supposed to maintain a gap?

When mine opens it opens fully, but when it moves to the closed position it leaves a 3-4mm open gap.

It's not dirty or sticking! That's just where it "shuts" to - with the 3-4mm gap so that it's not actually fully shut.

ilikemy944 · 05-21-2009, 11:08 AM

I can tell you that every ISV I've blown through lets some air pass.
Is your TPS adjusted properly? Supposed to 'click' just before the throttle gets to idle position. This is the most common cause for a high idle.

mallard ducks · 05-21-2009, 01:02 PM

hey Brad,

I figure it would still let some air pass in the closed position, but closed on mine is actually a 3-4mm open gap. I'm wondering what's up with that?

My TPS tests good for closed throttle and WOT and is adjusted properly - it may still be functioning out of spec as I've got some symptoms of that like sometimes having a flat spot on acceleration at about 3,000rpm. So I'm going to replace it regardless.

I'm just having a hard time believing that the proper ISV closed position has such a large opening ?