Idling problem

[Stan7600]

I have a 2001 Yamaha 4-stroke 115 that doesn't idle right. Runs fine at any speed above idle and I can go 1/2 throttle or faster half way across Winnie for example, then throttle back to idle and it will kill. It's been this way since a year old. Dealer can't find any codes. I've tried new plugs, Seafoam. Has anyone seen this before or have any ideas? I plan to try a different dealer this spring and see if that helps.I think I need a mechanic that will put it in the water and make the problem happen. Thanks! Stan C.

[marine_man]

On a EFI Motor idle problems are pretty few and far between... one thing you could check for would be an air leak between the fuel tank and the motor, but I would anticipate that if that were the issue you'd have problems besides just idle. Other than that, it could be a electrical gremlin... hopefully your new mechanic will be able to pinpoint the issue. Is the issue repeatable, or does it only do it once and a while...

marine_man

[boatfixer]

Another possibility would be the filter inside the VST (vapor separator tank).

[Stan7600]

Thanks for the replies. Yes it is repeatable. Once I had it kill 6 times while my partner was backing the trailer in. it will ALWAYS run great at any speed above idle, never misses a beat. When it kills it always starts right up again. I'm starting to wonder if the idle speed is too low. It runs about 800rpm at idle according to the dash tachometer. Not sure how accurate that is.

[Ballyhoo]

have them check the tps (throttle position sensor) and make sure it is set right. If the ECU thinks that the throttle is in a different spot than it is it can cause this.

[Stan7600]

jkb, Thanks for your input. I'll mention that when I get it in this spring. Stan C.