496 iac!!!
 

I had an IAC output fault and replaced iac and now the duty cycle at 650 rpms is 0% and if you rev it it will jump up to 99% then at idle will slowly fall back to 0%. I have a rinda scan tool and doing the iac test there's no change in rpm. checked all wiring and everything seems fine, boat idles fine but at 0%.
Could my ecm be bad? i can choke off the hose ran back there and idle drops, am i just misunderstanding duty cycle, as the boat idles fine..

fixx
 

did you clear the codes? might be stuck in limp mode and all it will see is o% to 99 %..clear the code and go run the boat and put a load on it,,it should correct its self.if not then their may be a vacume leak else where.

Thats exactly the way a 496 IAC is suppssed to operate!
The IAC counts increase when you back off the throttle the IAC opens to keep a smooth transition air supply into the engine while the rpms come down and keep it from surging or stalling. When its back idling at 650 rpms the IAC counts go to 0 becuae its not needed and it waits for its next needed operation.
It ain't broke don't fix it! Quit tinkering and enjoy your boat!

Best Regards,
Ray @ Raylar

the only thing that is bothering me is that using my scan tool i cant run the idle up and down it just stays steady no matter what you put it on, and i still have to change the gimbal bearing and waiting to get my sunpad back....

The IAC only comes into play when there are quick changes in throttle position where maintaining a smooth transition to idle condition is needed.

Best Regards,
Ray @ Raylar

thanks for the info raylar feel better now knowing how it functions that its working properly!