200 Idle Issues--(turns off sometimes)

Honda 2003 200 hp runs great, but at times when I let off throttle and put in neutral, engine will sputter and turn off. I have changed all filters, including high pressure filter and screen in VST, cleaned IAC screen, but didn't change the way it reacted..ECM is not giving me any trouble codes..any ideas?

Well, here is a real SWAG, but worth trying. Bypass your emergency cutoff (kill) switch.

Actually the emergency kill WAS cut off and I still had the issue? Could it be a faulty IAC?

Yes, could be the IAC. You said the ECM was not throwing off any codes, correct? (That is, you shunted the red four-prong service connector, and got no blinks on the MIL light?) If the IAC was the problem you should get a code 14 - one long blink followed by 4 short blinks.

I keep thinking you may have an electrical problem, specifically a grounding problem. You are coming off plane, slow down, and put engine in neutral, then it dies. Is that correct? If so, I would suspect something in the control box. That's why I initially thought the kill switch was grounding out. What specifically do you mean that "the kill WAS cut off?" Is it totally disconnected? Could it be grounding out?

I was trying to reset ECM a while back and the toggle was not connected, the splice was corroded...so I respliced it and kill toggle now works..Engine does not shut off every time I let off throttle, it varies..

I guess I'm out of ideas. Intermitternt problems are the most difficult to diagnose, especially from afar, and with no codes off the ECM, I don't know where to start.

Here are a few thoughts on the problem. The engine is running fine at speed, so it is unlikely a fuel feed issue. There would be plenty of fuel in the VST tank to keep the engine running for a while at idle, UNLESS your HP fuel pump is crapping out, so I would check and clean the connector to the pump. An air intake problem would show up at high speed, not low speed, so that doesn't seem to be the issue. A typical fuel feed issue would also likely show up a high speed. and not at idle, so that seems off the table. I keep going back to an electrical issue, a loose wire somewhere that is sometimes failing when you come off speed.

Just a recap...I've replaced main wire harness, checked grounds, also have replaced all fuel filters, including one that is unseen unless you remove alluminum intakes (more like a strainer). I have also replaced high pressure pump.

You seem very knowledgable about the engine, so it will be a bug hunt on your part. I'll keep thinking about this one, but at the moment I'm stumped.

Maybe someone else can kick in with some ideas.

Knowledgable by force..lol only because I had to open up engine, do head work, fuel pumps etc. But now I feel quite comfortable with this Honda engine..To me, its gotta be a sensor or a "setting"...so I come to the pros and ask away..Thanks for all you guys out there who have walked me thru my repairs