High idle after start

[Jemison Richard]

This is interesting to me as I have a Saturn that is screwing up (efi
problems I believe) and the main symptom is very low idle.  I got IAC codes
from the ECU and (being very new and obviously ignorant of these little
critters) jumped out and bought another IAC.  Didn't do squat.  I've checked
for vacuum leaks (spraying starting fluid all around the injectors, manifold
plenum, vacuum lines, etc.  Nothing.  I believe this system is a MAP based
system.

It runs great, accelerates and top ends best of all its range.  Coming to a
stop it does OK until you fully stop and sit there a minute.  Then the idle
drops down to 300 and the car dies shortly after.  I've tried increasing the
idle by turning in the idle screw (1- 1.5 turns) - nothing.  More than that
and it really starts running bad.  I can keep it running by holding my foot
on the gas while holding the brake on with the car in gear.  But this causes
the car to heat up very quickly.    Also, as it sits around 1000 rpms
(running steady at first) the longer I have to sit at a light the more it
starts jerking (like missing).  It is now starting to do this a bit during
50-60 cruise also.  Minor at these speeds but wasn't there a day or so ago.

As a side note (and I have no idea if this has anything to do with the
problem) I'm losing water (not much but a little).  Could be going out the
overflow from the heat ups.  Not sure.  I'm not leaking it.  That I do know.

Yea I could take it to a shop and get it fixed.  But if I'm going to try to
modify one of these things I have to know how it works.  And I should be
able to diagnose problems with it.  Otherwise how will I be able to tell
what to change?  So, any help would be appreciated.

Rick J

> -----Original Message-----
> From:	Jason Weir [SMTP:Jweir at worldnet.att.net]
> Sent:	Saturday, October 10, 1998 9:44 AM
> To:	diy_efi at efi332.eng.ohio-state.edu
> Subject:	Re: High idle after start
> 
> Gregory A. Parmer wrote:
> 
> > > Possibly.  Have you driven the vehicle?  Quite often, the speed
> > signal
> > > must exceed ~32mph before the ecm will try to reset the IAC.  At 1k
> > RPM,
> > > with temp > 180 deg, ECM should be trying to bring idle rpm down.
> > > Shannen
> >
> > No VSS yet. I don't think Jason's Jeep has either. One day, when I
> > understand this better maybe I'll understand how this info and Ludis'
> > info tie together to explain how/why this thing operates the way it
> > does.
> > It'll be a while before I can get the VSS signal going so I'll drop it
> > for
> > now. Thanks guys,
> 
> Exactamundo... No VSS but I have finally broken down and decided to go
> the route of the purist and I am gonna add one to keep the system as GM
> designed it... Well except for the EGR valve that is....
> 
> --
> Jason Weir
> 88 Wrangler - 258 Chevy TBI
> Fayetteville, North Carolina
> http://home.att.net/~jweir/tbi/inject.htm  --- TBI Installation Page
> mailto:jweir at att.net
>