IAC longevity problems

[MJones]

Hello, all:

I have a Holley Projection 4D in a marine application which works very well 
except for one bothersome problem:  I can't keep IAC motors alive for more 
than a few hours.  The IAC used on the Projection is common to Chrysler 
and, I think, GM applications.  The second one just trashed after about 4 
hours of engine operation.  Both failed the same way.  Electrically it 
seems to work fine, but the threaded rod attached to the pintle seems to 
cock and stick.  Wiggling it slightly frees it up until the next time it 
sticks.

I've checked the obvious things.  It's not binding in the throttle body, 
causing it to wear.  It dosn't get terribly hot, since everything, 
including the exhaust manifolds, are cooled to 160 degrees.

Is this a common problem?  I wouldn't think so based on the number of them 
in service.  Any ideas or suggestions?  Did I just by coincidence receive 
two defective ones?  Holley is no help.

Thanks,

Mike J.