Car dieing additinal info.

[Roger Heflin]

On Tue, 10 Aug 1999, Ward wrote:

> IAC's typicaly stick where ever that are at the moment.
> 
> The motor is a 2 phase stepper motor the is on a jack screw shaft.
> 
> The 160 steps for open is typical for a car, the compter commands the IAC to
> this position after key off, (the ECM runs for a few second after shutdown).
> 
> 
> On start up, the IAC moves rapidly to a value looked up on a  steps vs
> coolant table. 
> 
> After specific qual's are meet the IAC will go into ist own closed loop
> mode, regulating RPM looked up from a new table, RPM Vs. Cool. Late vehicles
> have 4 different target RPM tables.
> 
> I recomend that you check your MAP in gear and out of gear, S/B 35 - 40 Kpa,
> about a 5 kap diff in Vs out of gear. 

I will check this tomorrow.
> 
> This probelem you describe is not typical of any IAC failue I've seen. More
> like a Vacuum leak. 
>
If I had a vacuum leak it should bring the rpms up from too much air
getting in?  Or in some cases could it not be detected this way.   

Right now (after the new IAC) it only seems to die if f it is both in
gear and the AC is on.  I am hitting some pretty hihg pressures in the
ac (245psi), and I have noticed that the map runs 17-21 at idel, I
don't remember how much ift idfferened in gear vs out of gear.  If I
manually control the revs at stoplights and such it has not
difficulties, I just cannot figure out what changed.   The only things
I can come up with is that the tranny is loading things more or the AC
is loading things more , I just cannot come up with things that would
cause this.   

I guess another choise is that something is going on with the engine
that is causing it to run differently. 
 
> I would also check fuel pressure. Do theis with the key on and motor off.
> System should hold pressure overnight. 10# drop in 5 min's is a fail.
>
It only seems to have difficulty at idel, things seem just fine at wot
and part throttle, but coming off of idel seems to be an issue, would
a fuel problem manifest itself in this way?

 > Ward
> 
> 
> 
> 
> 
> 
> On Tue, 10 Aug 1999 10:33:06 -0500 (CDT), Roger Heflin wrote:
> 
> > 
> > I have noticed  that whatever is going on with my car dieing, that it
> > does seem to be alot more troublesome when it is hot outside (100
> > degrees) over when it is cooler (say 80).
> > 
> > I should have new IAC tonight, and it is pretty trivial to install it,
> > so I should know if that fixes it tonight.
> > 
> > Now on the IAC 160 is open and 0 is closed, where is it on startup and
> > which way does it usually fail (open or closed), or can if fail either
> > depending on why it failed?
> > 
> > And if it  is slipping, then that would imply that if the computer
> > kept signaling it to change (even though it thinks it is a 0 or at
> > 160) that it would offset the slipping, and possibly make things still
> > idle even with a bad IAC, at least until it gets so bad it does not
> > move at all?
> > 
> > 		Thanks
> > 		Roger
> > 
> 
> 
> 
> 
> 
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