Kelly O

Have an 03 575sci w/140 hrs. Boat has been sitting a while. At start-up, motor gradually revs up to 2000 rpm and will not come back to idle. Shut off engine and restart then it idles fine. It idles high like that at some start-ups but not every time. The shut-off and restart corrects it every time.
Any thoughts ? Fuel treatment did not seem to help.
Idle air control ?
Can take to scan if needed.

BillR

Idle air control - sounds like it needs adjusting OR your rear throttle body linkage may be sticking open a tad.

mrhorsepower1

Good point Bill. Agreed.

Kelly O

Thanks- I will check for the linkage sticking. Not sure if IAC would be out of adjustment since it is intermittent.

Shah Mat

How do you adjust the IAC? I didn't know they were adjustable

mrhorsepower1

Sometimes they get gummed up and will stick and need replaced. You do not adjust the IAC, you actually adjust the throttle blade opening.

BillR

110% correct

TylerCrockett

Your iac motor will open when you give it some throttle you will see the iac counts go up. Also if the engine is not getting enough air at idle the iac will stay open. I would turn the key on with the throttle all the way shut, engine off and check the voltage at the blue wire on the throttle position sensor it should be .500 Sometimes you need to slot the holes in the sensor to adjust to the .500 You also need to start the engine and get the minimum air rate to get the Iac counts at 5-20 counts then make sure your throttle sensor is at .500 When you change the idle you are changing the throttle sensor voltage. Tyler