Cadillac Repair: stall at ide, carbon buildup, wire connections

Question
work was done by ase mechanics  so i doubt that is it  i have narrowed it down to crank sensors or ignition module,  but no code from either  how do we test them
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Followup To

Question -
I have a 1997 northstar deville nad have been having trouble with it stalling at idle, doesn't run rough it just dies as if you turned off the key 146,000 miles. It does to seem worse after 30-45 minutes of highway driving. Changed the iac but that didn't help. Changed the water pump and problem went away for awhile, thought the belt may have been throwing water on a connection causing the problem but i guess not problem returned yesterday while in the drive thru @ mcdonalds twice, got home and it did it twice in the driveway  any ideas?

Answer -
Like you read in some of the answers, Thes possible faults are endless. It can be a carbon buildup in the EGR valve. It could be that you did not preset the IAC valve before you installed it or you did not clean out the passage hole with some aerosol cleaner before installing the IAC.  Without having physical access to the vehicle to get a feel for the way it stalls there is just to many possibilities to list that it could be.

Answer
Are you getting any codes from the computer ?. Do you know how to access them ?.

Reading your question you said that AFTER you replaced the water pump the fault went away. It is highly likely that you disturbed some of the wires in the area where you were working. Look around and check all the wire connections that you may have touched or moved.