IAC not working on 1986 E150

1986 Ford E150 Van V8-302 5.0L
DTC's 12 and 13 are set. IAC is not working. Stalls at idle.
Have already replaced PCM and ISC motor. Have already checked all pins for continuity and shorts to ground.
Guess is that the problem is electrical, and not mechanical. Any suggestions what to try next?
I am posting this for a friend who does not have internet access. So I may not respond to help right away as I have to do a go-between thing. But all help is appreciated, even if I am slow in responding.
Jim S.
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How about the vacuum lines, have they been inspected? Throttle linkage is not binding?
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wrote:

your throttle body is gouged or cracked
hurc ast
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