Re: [DML] Tuning idle speed circuit

["therealdmcvegas" <DMCVegas@xxxx>]

--- In dmcnews@xxxxxxxxxxxxxxx, "Jerry Harry" <jlharry@xxxx> wrote:
> Well, My problem is not the vacuum its the idle speed motor.
> Do these things have a failure history. Mine no longer hums when it
should
> or always did in the past and my idle no longer works at all.
> When I start it up it will run if I give it some gas and keep it
running
> that way, if I let it drop back to idle it will just die, makes no
attempt
> to run. The idle switch is working and I have voltage on the motor
plug but
> the motor does not turn, nor have that little hum it had when all was
> working.
> John, Martin, David, what do I check next? Is it time for a new idle
speed
> motor?
> Thanks for any input.
> Jerry Harry
> Vin# 4890

Checking for voltage on the plug that connects to the Idle Speed Motor
is a good start, but it's not everything that you need to do. More
importantly, you'll need to check for solid continuity on all 3 wires.
Use a Voltmeter, and check that when supplied with a full 12V, each of
the wires is able to pass said voltage thru with minimal resistance. I
had the EXACT same symptoms as you, and found that the one of the
wires wasn't passing full voltage. When tested, it was only
registering 8V or so. I grafted in a new wire in it's place, and the
Idle Speed Motor ran just fine.

This procedure isn't difficult at all. You just need to remove the
access panel behind the drivers seat, and the Idle Speed ECU is right
there on top. Pull the 2 plugs (checking of corse for corrosion, and
cleaning the contacts if nessisary), and utilize the 12V feed wire
there as your source for testing power. While you're at it, you can
also check the ground connecction, and the Microswitch to verify that
ALL will allow the full 12V to pass thru them.

You know that the engine will not idle because it doesn't have the
airflow to keep running. And while the ISM is the prime/logical source
of failure in this case, you don't know for certain that it is the
root of the problem, and not something else in the Idle Speed Circuit.
To check if the motor is rusted into place, simply remove it, grip it
like a doorknob, and shake it back and forth. You should hear a loud
"CLICK!" "CLACK!" from the the valve/impeller assembly inside as it
freely spins, slapping the metal stops that limit is movement. If not,
then you'll know it's rusted.

It most definatly is much more work than simply replacing the Idle
Speed Motor. But becuase I skipped this step, I wasted some good cash
on unessisarily purchasing a new ISM. Of course, since I had a new
ISM, I got to gut the old one to see just how everything works inside
(check the archives from about 2 years ago for a post I wrote that
explains the entire Motor/Circuit function in detail).

-Robert
vin 6585 "X"