GT40 high idle at warm temp

[todda]

Hey all. I could use your input. 1999 SN w/GT40, only 240 original hours. Put it in the water today, started normally, ran it up to 160° temp, but when we throttled back to neutral, it stayed at a very high idle (2200 rpm), and wouldn't settle down into normal idle. Shut it off, let it sit for 20'. Started back up at "normal idle," but as it idled, continued to climb up to 2200 again. So...something seems temperature related. I have replaced the TPS about 2 seasons ago, so I am doubting that (and, seems that would have nothing to do with temp either). Any thoughts? My inclination would be a temp sensor? Thanks for any guidance!
Todd A

[NautiqueJeff]

Does the boat have PerfectPass? If so, my bet would be a cable adjustment there. Here's what PP says about this issue:

Turn PerfectPass black dial on Servo one full turn counter clockwise, then start engine and if idle is now normal the PerfectPass linkage needs adjustment. Every time PP is powered (Or boat started) the Servo does an “Auto Tighten Rotation Check” and attempts to turn the dial clockwise which is normal. If the adjustment at the Brass L is not right (A gap) it can close this gap and open the throttle. With key OFF, try turning the Black Knob clockwise until snug and you may see the Throttle Arm on Engine open a bit if there is a GAP. See Figure C. (With boat in Neutral, make sure No Gap Here) The location of the Brass L Adapter must be adjusted along the threaded portion of the cable to remove any gap. Then try turning the black knob again and confirm the boat throttle arm stays at the dead idle stop. The only adjustment for PerfectPass is where the Brass L attaches to the cable.

A temperature sensor will have nothing to do with this issue.

[todda]

Thank you NautiqueJeff. Yeah, I have PP SG with ZBox, and I had already checked that adjustment. No gap between the hex nut. So, I am onto next steps of problem solving. I am going to clean the Idle Air controller next, see if that resolves the problem. Very odd, as it seems to be an issue with it coming up to operating temp, as the idle is fine when the engine is at cold start.

[Jonny Quest]

could also be the T-P-S (throttle position sensor) going wonky with heat.