2002 Honda 225 Idle

So I have searched and read numerous posts on this forum and others and still cannot solve my issue.

2002 Honda 225, 1490 hrs, compression is 190-205 all cylinders, all filters new, new injectors, new fuel pressure regulator, fuel pressure 46 psi, new IAC, new IAT, new HO2 sensor, new ZFR6FIX-11 plugs, leak-down test was good. Upgrade to the exhaust tubes was done back in '06, new t-stats in '10.

The engine has a miss at idle(runs rough) and reving in neutral the miss(sometimes a pop) continues.* The engine will rev, have taken to 4k rpm in neutral.* Do not notice the miss when the engine is running under load, doesn't mean that it isn't there.* Sometimes when reving the engine, when I bring it up to say 3k rpms and try to hold, the rpms will drop 400-600 rpms and never reach 3k unless I advance the throttle.

The only Honda dealer here is stumped, they performed the fuel pressure test and read the codes(that is when the IAT sensor was replaced).

Also, I just noticed that the plugs that I replaced are a different stock #6441(new) vs 4095(old), both iridium plugs with similar numbers..............I do not have the original plugs that I took out.................maybe this is the culprit??

Any ideas/thoughts?

Thanks.

Yep, that is likely the culprit. Use only NGK IZFR6F11.

Follow up - If you change out the plugs and that still doesn't solve thr problem, Then closely inspect the coils for loose wires ar a corroded connection.

Okay. Plugs changed and the idle seems a little smoother. Coils look good no corrosion, wires look and feel in tact.

A couple more questions: how much fuel is supposed to be in the low pressure filter bowl? The level of the fuel in the bowl now is just above the bottom metal rim of the fuel filter. Fuel seems to trickle into the bowl when the engine is running., is this normal flow?

No. Normally, the low pressure fuel filter should be full, or very nearly so. Under heavy load, it may go down a bit temporarily, but normally full. See your owners manual.

So let's back up from there. Remove the LP filter, clean out the bowl and inspect for water and debris. Make sure the rubber bowl seal is in good shape and properly seated. Inspect the top of the filter body for cracks or corrosion. As you reassemble, make sure the two hoses are clean and air tight. Make sure the rubber suspension strap is aligned properly as shown in the operators manual.

Next back up to onboard fuel water separator. Do the same thing. Normally, that filter is not changed out, but if it shows signs of deterioration or clogging, or if there is a lot od water and debris in there, replace it. Inspect the hose between the fuel water separator and the LP filter bowl for cracks and corrosion. Then, use your pump-up bulb to recharge the system with fuel. Both bowls should fill up and there should be no leaks anywhere. The bulb itself should get very firm after the bowls fill up. If not, replace it.

I assume you have an external fuel-water separator - a Racor or similar. Again, inspect the fuel line connections at the Racor to make sure they are tight and there are no leaks. Drain the Racor and inspect the bowl for excess water and debris. Replace the filter if it has not been done recently. Should be replaced every season. When reinstalling, make sure that everything is tight and well sealed.

If none of that fixes the problem, there are two other tests. Run the engine and see if the pump-up bulb becomes partially collapsed. If so, you have a clogged fuel tank vent or a clogged fuel pick up screen in your fuel tank. To test for a clogged tank vent, simply open the tank filler cap and see if the engine runs better. If you suspect a clogged pick up tube in the tank, blow low-pressure compressed air back through it to see if it clears it temporarily.

The other test is to run a clear plastic tube from your pump-up bulb to the on-board fuel/water separator, run the engine, and look for air bubbles.

Okay, I have done all the above. I even removed the fuel supply line at the onboard water/fuel separator and hooked up to a separate tank to bypass the supply system on the boat. Same results. I can pump the bulb to fill the LP filter bowl, but as soon as I stop, the fuel level drops. The engine does not smooth out when pumping the bulb or when the bowl is full. I am beginning to think the LP pump may not be pulling enough.............

Yes, based on that, and all the other stuff you have done, it sounds like it's probably the LP fuel pump, which is not difficult to change out once you get the intake manifold off.

Okay, low pressure pump replaced and the fuel cut solenoid. Hard start issue resolved, fuel level in low pressure bowl stays about half full at idle or rev'd up. Idle still not smooth. Now when I rev it and hold rpms the engine will act like it's starving and rpms will drop. Also when I return to idle suddenly, the engine dies. Now I think the issue is VST or high pressure pump related(just replaced the HP last year and rebuilt the VST the previous year). The only thing that I am not sure about is the float adjustment of the VST, I never checked it during the rebuild. This engine is a major PITA, since plugging the HP filter two years ago, it has not run right. There are NO good Honda mechanics within 100 miles of me and I just want to get this thing running, so that I can sell the boat!!!

I'd check that HP filter again. Be sure to check or replace the O ring. If you do not have a replacement O ring, use a little vasoline on the O ring. Can't help you on setting the VST float - don't have access to may shop manual today. But will get back on that as soon as I can. I'll also get back on the proper fuel Pressure you should have.

Okay, ran the boat today after having the ECU replaced. Runs great! The old ECU was not reading the IAT.

Now I just need to replace the shift and throttle cables.

Good deal. Glad you got it running right. You went down a lot of trails to find that problem.