5KSQ High Idle - Idle Stabilization Valves (ISV)

[Ben Swann]

[Someone wrote a few weeks ago that they had a high idle problem on their
5KT
that was fixed by replacing the ISV.  That person stated that they knew the
ISV was bad because it was easy to blow through it.  Others chimed in that
their high idles problems were fixed by replacing ISVs that would not
completely close.

I don't believe that this is the test for ISVs.  I don't believe that an
ISV
for a 5KS (Don't know about the turbo.) closes completely.

Any more opinions?]
No Opinion - the turbo one is a two wire, and should not pass any air.  Now
a marginal one, which passes a tiny bit will work ok with a properly
seating idle screw turned almost all of the way in.

These things a bane.  I have 5 of the turbo ISVs, and all except one pass
air.  One just drove me crazy while trying to break in and get the motor
running right after I rebuilt it.  The problem(s) were compounded by a
bad/hard O-ring in the idle screw.

Some of the other units are 3 wire, and perhaps some of the 2 wire units
reverse polarity to get the valve to close.  In any event, these are an
expensive piece to replace, despite the fact they can last for 100kmi or so
IMO.

Ben

[Huw wrote -
"some" ISV's rest position apparently is "closed" - two wire ones?
maybe.

"other" ISV's, eg the ones in n/a type 85/89 cars, have a rest position
about 1/4 open and flap open and shut when triggered.

the test would be more like running a few (5?) volts across the pins and
making sure they open &/or shut properly without sticking.

and that your harnesses are all well grounded, etc.

--
Huw Powell]

That is good information..Ben