Excellent info. Thanks, John.

So, I should be able to test signal from the TPS at the ISCU connector?
Anyone know which pin(s) that is?

On Sun, Jan 24, 2010 at 12:04 PM, John Bange <jbange@gmail.com> wrote:

>
> So, I'm left wondering if the ISV effects cold start. I think that it must
>> as its function is to add air to the mix at the throttle, yes? So, if it
>> isn't functioning and it is not adding air at cold start, then opening the
>> throttle slightly at cold start is allowing the needed air into the
>> throttle. Does that makes sense?
>>
>>
> Yes, spot on. The idle controller watches the throttle switch and adjusts
> throttle bypass air to keep RPM within a certain range. Standard tuning
> procedure is to disconnect the idle stabilizer and set the bypass air on the
> throttle body so the engine idles in the normal 850-ish range when warm, so
> a warm engine theoretically doesn't really even need the idle stabilizer.
> Cold engine, though, can definitely have trouble without it.
>
> I suspect that the ISCU is kaput. Is there no way to test the ISCU itself?
>> I
>> haven't any method described in any of the manuals. It's an expensive part
>> to swap in on a hunch.
>>
>
> If the ISV isn't "humming" with the key at ON and the engine not running,
> something in the idle control system isn't working. The valve is controlled
> via pulse width modulation, so when it's doing its job, it'll be vibrating.
> It's unfortunately not all that uncommon for the controller to crap out.
> Still, I'd check all the wires first, make sure the controller is getting
> 12v, it knows the throttle position switch is closing, and its connection to
> the valve is OK before buying another controller.
>
> --
> John Bange
>
>

--
mordo
1990 Carat