IAC longevity problems

[Shannen Durphey]

MJones wrote:
> 
> Is it critical, then, that the IAC never be allowed to reach the ends of
> its travel?  What happens to the IAC motor if the throttle blades are set
> such that the idle rpm can't come down into control range?  The IAC would
> go full closed.  Would the IAC motor be damaged by this?  Similarly, the 4D
> opens the IAC a fixed amount during each start sequence.  No matter where
> it was when last operated, it opens it further.  What happens to the motor
> if, when tuning/adjusting etc. you crank the engine over several times in
> succession but never start it.  The IAC goes open further each time until
> reaching the end of its travel.  Would this damage it?  If so, how does GM
> handle this scenario?

The IAC *should* bottom out before it is overextended. 
Mismatched IAC, incorrect machining, possibly too thick
gasket on the base could cause problems.  If minimum air is
too high, IAC will extend pintle fully in GM system, and
full extension is limited by depth of the passage.  Then the
ecm can tell when the end of travel is reached, and stores a
value for minimum IAC counts.

> 
> Beginning to sound to me like the closed throttle angle must be set such
> that the IAC does not go full closed, and that the IAC be disconnected
> during fiddling.  Any other ideas?
Put a daub of grease on the end of the pintle.  Install (
very carefully) the IAC with the pintle extended, see if
it's bottoming out and marking the grease. You should be
able to tell witthout applying too much force to the
screws.   Find another ProJection to compare it to.  Another
possibility, although not likely, is that the IAC was
extended when installed, and forced against the seat too
hard, damaging it.

Just some thoughts.
Shannen
> 
> Mike Jones
> 
> Bruce Plecan wrote:
> 
> Sounds like the distance from the mounting "face" to the orfice is
> too great allowing the pintle to be hyper extended, and too much of a load
> for the stepper motor.    Might try to find out how to extend it,
> installed, and record that lenght, and compare it to someone else's
> That's all I can think of.
> Cheers
> Bruce