re. High idle, problem with idle air motor

[Ben Swann]

Well, I was going to suggest that the idle switch circuitry has a fault, but if
disconnecting the switch only makes it worse, that tells me that the problem is outside
of the idle control circuit.  There must be an introduction of extra air into the
system.

With Megasquirt, the engine will continue to run - albeit at higher RPM as more air is
introduced.  Must be a leak in the intake manifold or a disconnected line.  With MS,
there is no metered air before the throttle and engine runs based on how much throttle
is opened, or if there is a leak then as if one is stepping on the pedal.

Trouble-shooting for this problem, I surmise, is different than for an engine still
running on CIS.  However, I bet the problem is easy to find and resolve.  Just look for
a disconnected vacuum line or any air leak after the throttle - or the throttle itself
is allowing more air to pass.

ISV is still suspect.  I'd substitute something to totally block flow in place of the
ISV in order to rule it out.
:
:
Now I re-read the post.  Puts me back to suspecting the ISV circuitry and Throttle
switch is suspect and I think a re-check of the switch is in order.  Is this a one
switch or 2 switch setup?  He may have disconnected the wrong switch.

Or - the both ISVs are bad.

Might help to understand the setup better - what ECU, which Idle control system, which
ECU used for ignition?

For ex.  My car uses the MAC-14 for ignitions and MS V2.2 Extra for fuel and has no ISV.
That's right, I have had no need to install an ISV since once the engine warms up after
a few seconds, idle is rock solid.

Ben

[Date: Fri, 7 Mar 2008 19:07:00 -0500
From: "Eric Sanborn" <eric.s.lists at gmail.com>
Subject: High idle, problem with idle air motor
To: Quattro <quattro at audifans.com>
Message-ID:
	<19b644240803071607h3252fe7bx7616dd74477e8556 at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

Last week I sold my 4ktq that I have been driving for going on 8 years
(4.5 years as a turbo).  Over all that time I had no problems with the idle.  I guess to
punish me for selling it it is acting up for the new owner.  He starts is up and it runs
up to about 2200 rpm and won't come back down.  Other than that it works well.  He is in
NJ and I am in VA so I can't exactly go help him in person, but I want to help him
getting it running right again.

The patient is a 1985 4kq with a 1985 KH turbo engine out of a fwd 5k.
 It runs megasquirt for fuel, but still uses the KH ignition and idle control.  I had
the new owner take the idle motor off the intake manifold and plug the hole.  It idled
properly.  So he swapped in another motor he had and it started idling very high again
even on the new motor.  He tried spraying them with carb cleaner, same result.  If you
unplug the idle switch on the throttle body it just makes the rpm go higher.  If you
unplug the idle motor nothing changes.

It seams to me that something other than the motor is out of wack since two different
motors give the same result. I have never had a problem with this system before so I am
not that familiar with its operation.  I have looked over the 4k manual and didn't find
anything that jumped out at me.  I have not found my 5k manual yet (moved last summer
and still trying to find stuff).

 Does anyone have any ideas?

Thanks in advance!!

-- 

Eric Sanborn
http://sofadog.net/projects/]