atestani123

This is a post-drive by wire so there isn't an IAC. I wish I would get a few DTCs! Not having any is making this hard. I appreciate the help because at this point I am baffled. I agree with testing parts as you say but except for the throttle potentiometer which was really sloppy and suspicious, all the rest of the stuff was needed maintenance anyway. However, I am having some new symptoms that are starting to worry me about this being the ECM. Today, I had a couple of starts where the engine would rev up an extra 500 or so RPMs and back to normal idle and repeat this several times 3-4 seconds apart before settling down to a smooth idle. Two other times I would have it at, say, 2500 RPMs and slow down to take it out of gear but the engine would just keep on rev'ing. I had to shut it off to make it stop. When started again it was normal. I may have to break down and take it in to get a Diacom connected to check this out in more detail.

Thanks for the information! Where is the IAC located on an EX343?

I am out of ideas on this problem and would appreciate some advice! The symptom is that when putting the boat in gear (forward or reverse) the engine will intermittently rev UP all by itself and settle down as well... enough to knock someone off the platform! It seems to have gotten worse as now when it revs up the driver needs to pull the throttle back to stop it. Fuel being used is the same I have used for a long time and from the same gas station. Other than this issue the engine/boat runs fine. I haven't been able to correlate to engine or ambient temperature, whether it is the first or second set, etc.. Here is what I have done to no avail: - replaced both fuel filters (drained FCC) - Set timing to 8 (latest spec as far as I can tell) - checked fuel pressure - rock solid at 60psi - Checked for DTC codes - none - replaced distributor cap and rotor - replaced the potentiometer/throttle position sender - replaced the throttle cable - verified the problem is there even if ZO is off - tested with several settings of throttle cable to potentiometer "home" position Anyone have any advice on how I can correct this problem???? Thanks! Al