IAC problem solved

[M. Jones]

Well, took the boat (with the 4D system) out of storage last weekend and tuned 
it up.  Had a problem last season with intermittent 'failures' of the IAC. 
 Sometimes the IAC would freeze and idle would be way high or way low.  Shut 
down and restart the engine and it would be O.K. for a while.

Finally had enough time to  properly troubleshoot and found that the IAC system 
was actually fine.  Hysteresis in the TPS (which tells the 4D to go to idle 
mode at 30 degrees throttle angle) as well as in the throttle linkage would 
occasionally not let the TPS get to 30 degrees.  The ECU therefore was still in 
run mode, and so no IAC activity.  Set the closed throttle TPS position to 28 
degrees and problem solved.  Nice when things work out!

Mike J.