Idle problem

[jmills321]

Hey Guys I need some help.

I have a 2007 DF250 that has had a problem with not idleing down when pulling back on the throttles. The motor only has 55 hours on it since new and I bought the boat from a guy that allowed it to sit up for 2 or 3 years with no run time. The motor cranks and idles perfectly on first start up. After running 30 minutes or so steady throttle, when I pull the throttle back it sticks at about 1800 or so about 1/2 the time. I can quickly advance and pull the throttle back and it goes back to the 650 most of the time. (like and old carburated car when they were choking and cold) I did have the IAC code awhile back and I replaced the IAC valve. I have never gotten that code again. This does happen most every time, but sometimes it does not happen the whole trip. I had all new throttle cables put in the boat (Telflex Extremes) recently, but that must not have been the problem. Can this be gunk or slug build up in the butterflies that could wedge the butterfly open just enough to not allow it to idle down? Again just a quick throttle up and down corrects the idle rpm back to 650.
Any thoughts or ideas to try? Seems like it should be something simple.
Thanks in advance

[jmills321]

No thoughts on this? Trying to figure this out. Any ideas?

[Moonlighter]

Check throttle linkages. Grease up and make sure they are moving freely, and that nothing was bent or damaged when cables were replaced.

It does sound like something mechanical from what you have described.

Also check the cable routes, there may be too sharp angles in them the way they were installed. New ones could have been placed the same as old.....

Good luck, and keep us posted.

[Solarman]

not idling down

Yes, you might check the throttle butterfly, disconnect and work by hand to see if it actually goes all the way back easily, or if it hangs just before the stop.
It may also be the cable adjustment.
And these newer motors also have a throttle detent that may be hanging up.it prevents motor from returning to idle immediately, just like cars.
Good luck.

[jmills321]

Throttle Detent

Where is this detent? Is it on the engine or on the control at the helm.

Thanks Solarman

[Solarman]

throttle problems

As with many autos the throttle detent was party of the throttle control system, usually located/ attached to the butterfly. It was designed to allow the motor to return to idle in a controlled way, to prevent surging. Many of the detent systems were controlled by vacuum, the newer motors added electronics, to allow rapid but controlled throttle return, mostly to allow timing, fuel system, o2 and electronics to remain balanced while the engine decelerated. if you have a good shop manual, it should mention around the throttle position sensor & around idle settings. It may be part of your tps, or butterfly. If it sat up for that long I'd be inclined to think it's sticking as well.
It might not hurt to try a penetrating lubricant spray on both sides of the butterfly stem, nothing heavy like grease, but maybe a silicon spray lube.

Good luck.