5KSQ High Idle - Idle Stabilization Valves (ISV)

[george mills]

On my 87 5kq NF CISE3 the ISV at rest is slightly open. If you run the
out-put tests with ignition on, placing and removing fuse in the fuel
pump relay, the ISV will close and open rapidly a few times. You can
also get this to function separately using a 9v battery. This is a
two-wire type ISV. There is a bypass hose that runs to the filter box
and connects before the air plate, ie. metered air. I believe on start
up the ISV is closed and crankcase/valve gases are routed to before
the air plate. When tuning you should plug both intakes to the ISV
from crankcase and valve cover, make sure the air mixture screw is
firmly seated (these things apparently were sealed at the factory,
mine wasn't anymore), and adjust mixture at idle when engine is at
running temp.
  Mine is starting to run rich so when the temp warms I'll get at it.
Just my back yard mechanic feelings on this...if I'm in any way out in
left field, you'll hear about it...pretty much guaranteed.

Best regards,
Geo

Christopher Ritchie wrote:
>> 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?
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.