Car dieing additinal info.

[Ward]

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. 

This probelem you describe is not typical of any IAC failue I've seen. More
like a Vacuum leak. 

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.

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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