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Re: [St] Still have cold start problem



Rup,

It doesn't sound like a stepper motor problem, but you can check it.  While you had/have it off, you can plug it in and either mounted or holding it, turn the key like you're going to start the bike.  During the ECU initialization/boot up the motor will be excited by the ECU and move.  Obviously, if it doesn't move, it's bad.

If it's not the idle stepper, I think the only way to test the sensors is with a diagnostic tool like the tuneboy.

FL-Rich


----- Original Message ----
From: Rupert Galea <rgalea@xxxxxxxxx>
To: st@xxxxxxxxxxxxxx
Sent: Friday, March 28, 2008 3:12:54 PM
Subject: [St] Still have cold start problem

A will back I made the post below. Basically I was having to give the
bike a bunch of throttle to get it started and then it would not idle
until it was warmed up. Once warmed up the bike runs fine. I removed
the stepper motor and the plunger was a bit dirty so I cleaned it and
put everything back together. This did not really help with the
problem.

So I assume either the stepper motor is dead or one of the three
sensors mentioned below is. I know the coolant temperature sensor is
OK as the gauge works. I assume that if either of the intake air
temperature and pressure sensors were bad the bike would not run well
once warmed up and/or the MIL light would be on. This is a 1999 ST
with 49,000 miles on it.

I am tempted to just buy a new stepper motor. Can anyone offer any insight?
Rupert

---------- Forwarded message ----------
From: Rupert Galea <rgalea@xxxxxxxxx>
Date: Wed, Oct 31, 2007 at 7:54 PM
Subject: Re: [St] Cold start circuit is no longer
To: ST@xxxxxxxxxxxxxx

Found this in Haynes
"Cold starting is controlled by the ECM which reacts to information
sent by the intake air temperature and pressure sensors, and the
coolant temperature sensor, and adjusts the fuel requirements
accordingly - there is no manual method (i.e. choke) for assisting
cold starting"

Since the bike runs fine once warmed up and there is no MIL I am
guessing these are fine.

Also from Haynes
"The idle air control valve is actuated by the ECM and set according
to information received by the ECM from the various sensors. The valve
is used to control the engine idle speed, to adjust the air supply on
engine overrun, to correct for altitude, and for cold starting. The
idle speed cannot be adjusted manually."

So it looks like I have a gummed up stepper motor.

Thank everyone
Rupert
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