the flyin' scotsman

With the high idle issues with the '90 GT and the subsequent 2nd pull of the intake I want to verify the ISV is absloutely in perfect working condition.

Anyone have a reliable bench test they could share?

Stromius

Think I read a 9v battery would cycle it without damage. I used acetone and ATF to clean it.

the flyin' scotsman

thx Stefan............is there a particular polarity?

928 at last

Hi Malcolm,
When I looked into it, the 9V battery test was about it.
The ISV itself is binary, on or off. Apparently uses pulsed signals to control the idle.
Mine was seized solid. (Not the usual situation from what I've read).
Hope this helps,
Rob.

928 at last

Nothing works. The only thing I didn't try was a torch.

the flyin' scotsman

thx Rob.

Did you use the 9v batt outta the torch?

blown 87

Replace it if you have any doubts out it and have it out.

The only real test is substitute with a known good unit.

Lizard928

If you put +12V to it (short duration), it should open fully.

Use brakleen or the like to clean it out.
I use graphite spray or the like to lube it up prior to reinstall.

tveltman

If it is PWM you may be able to use the built-in PWM generator on an arduino. The signal may not be strong enough, so you may also need a servo shield for it. The total package, pre-built, will probably run you 60 bucks, but then you have a PWM generator, so that could be useful...

the flyin' scotsman

I've wanted a variable power supply for sometime, especially a low voltage low current machine

John Speake

In normal use a 100Hz PWM square wave is used to set it to the required position. The ISV is spring loaded to the closed position, so battery will allow you to fully open it, then switch off battery and it should return to the closed position without sticking.

blown 87

It is hard to duplicate the conditions that exist under the intake with a ISV on a bench.

I would replace it if there was any doubt.

SQLGuy

Do any of the Bosch ones have embedded damper diodes? I have seen that on some of the Ford PWM IACs. If there's a built-in damper diode, you'll have to make sure that the polarity is correct when testing the unit... otherwise you'll just short the damper diode or blow your PWM test rig.

John Speake

I don't know if there is a diode in the ISV. I assumed that for testing, the tester would confirm from the WSM the correct polarity of the volts source to the ISV connector.

Lizard928

None of them have a flyback diode in them. But you will not hurt it putting the voltage on the wrong way.