f 115 efi revs jumping all over the place when in neutral.

[cobb3333]

Hi Guys,
Any pointers would be appreciated.Im in the process of getting boat and engine ready for season.I hooked up the engine to water point as boat is in my drive,the engine starts easy enough,but on idle it fluctuates up and down ,range 1800 to 2200 rpm ,then drops down to 600, /500 sounds like its going off a cylinder then stalls. I start it rev it slightly so it clears itself ,leave it ticking over and same happens again. I don't think it is a fuel problem.
Any ideas thanks. the engine is 2000 model

[ausnoelm]

IAC?? Idle Air Control valve? There is ways to test it, post the complete model number and someone will come along with help.

[greasyshaft]

Better yet have it plugged in a monitor the ISC request - will tell a big story to someone who knows what they are doing

[cobb3333]

Thanks guys, I wont get time to look at the engine again till the weekend,il let you know how I get on

[cobb3333]

Hello guys , latest update. I cleaned all the fuel lines and filters, removed the isc valve, on inspection everything was nice and clean. I sprayed it with carb cleaner and refitted . I plugged in yds software, Results when the engine was cold the throttle position was 1.4 deg, isc 60% 1089 revs. As the engine warmed up the isc reading came down slowly to 0% ,engine revs now 800 , everything seems normal. Switch off engine and restart engine now reving at 1725 to 1825, isc reading fluctuating between 73% and 100 %. Switch off engine and restart again isc 60% falling back to 0 revs normal.This happens intermittently. Do I have a faulty isc valve, or can it be something else. Before I spend out on new one as they are quite expensive.


Any advice would be mutch appreciated.