RE: [DML] Re: idle problems

["John Hervey" <john@xxxxxxxxxxxxxxxx>]

Group,
I get ask the question all the time about the Idle speed motor and I would
just like to say, yes it looks like a motor but it doesn't turn or
continuously rotates like a motor.
When the micro switch is tripped it completes the ground connection in the
circuit and the ECU sends more current to the motor to change the position
of the orifice in the motor, that's why it is a three wire connection.
The motor as we know it only rotates 180 degrees one way and 180 degrees
back. All it does is open the orifice and allow air to got into the air flow
meter so the car won't die.
In an idle position or when you let off the gas the vacuum solenoid closes
the vacuum to the ignition distributor so you won't have any spark advance
and the controlled amount of current goes to the motor to open the orifice.
I sell a few a year and have repaired a couple and the main problem is the
orifice movement may be stuck from moisture but won't move even though the
motor is humming. So don't think the operation is good if it hums. That is
what it is supposed to do.
One more thing, if you hook up 12 volts direct to the terminals in trying to
test it, you will or may burn it up.
As David said, the ECU very seldom goes out and I have one that can be used
to check out yours if you have a problem. I also have plenty of new ones and
good used motors if need. I don't mind loaning them out for test.
The temperature sensor switch also very seldom goes out because there are no
moving parts, it just changes resistance. It can be tested very easy for
operation.
Once you are idling good the bottom screw on the throttle body lever can be
adjusted to allow more air in to up the idle speed, but the top screw needs
to be adjusted also as to not loose the trip. The car idles better and runs
better at about 900 RPM's as far as I am concerned.
Our shop has just reworked 2 cars in the last week with idle problems and
neither one needed a motor or an ECU.
John Hervey
www.specialtauto.com
Now with a DeLorean shop.





-----Original Message-----
From: Dave Swingle [mailto:swingle@xxxxxxxxxxx]
Sent: Thursday, April 14, 2005 11:31 AM
To: dmcnews@xxxxxxxxxxxxxxx
Subject: [DML] Re: idle problems





I've seen (twice) high idle caused by complete failure of the idle
control computer (using the term loosely). The test was to unplug the
computer, then the car would idle slow and somewhat erratically.
Swapping in a known-good box was the diagnostic technique, mostly
because I had another one handy.

Dave


--- In dmcnews@xxxxxxxxxxxxxxx, "Warren Wallingford" <warren@xxxx>
wrote:
>
> The flurry of talk lately about idle control problems, especially --
-

> To check the idle motor, grab it with the key on.  If it's
vibrating, generally it's OK or will be. Spray some WD-40 into the
throat and give it a couple of firm raps with the tuning hammer. If
it's not humming, check the connection on top.  Peel back the boot to
see that none of the little connectors have backed up into the boot.
If by this time, the motor doesn't respond, you're in for an idle
ECU.  Also, there is a temp sensor that tells the ECU to let more air
in when the engine is cold-the Contant Idle Switch or Thermister.
These go bad in a characteristic way.  The engine will idle fine
until it warms up, then as the engine warms, will rev higher until it
settles into a 2000-2500 rpm idle.  The thermister is located in the
coolant distrubution pipe under the intake manifold.  It cannot be
unplugged or overridden exept by disabling the ECU.  This failure is
very irritating.
>
> After all this, if the idle won't be controlled, there is surely
extra air coming from somewhere.  Find it.
>
> Pictures for the idle motor, ECU, Solenoid and Thermister are
behind the links.
>








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