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2003 BF225 Revving Up and Down at Idle

D

dagostino82

Member
Hi There,

I have a 2003 BF225 that has had an intermittent revving up and down at idle and when the boat just is in gear out of idle. At any RPM higher than idle and just in gear, the revving seems to go away. Well lately, The revving at idle is more pronounced as if the motor wants to stall on the low rev. The motor is also stalling a lot when throwing it into neutral. My primer bulb has been installed with the arrow pointing down since day one. I thought that might be the problem so I flipped it to where the arrow faces up for the check valve, but that did not help.

- Fuel lines from gas tank are 5/16" A-1 15 and a couple years old.
- Fuel line and primer bulb from external water separator to motor is 3/8" A-1 15 and is a couple months old.
- Primer bulb is a little squishy when the motor is revving. Not rock hard.
- High pressure and low pressure fuel filters are a month old.

I think its a fuel issue but not sure what to check. Any suggestions? Thanks!
 
Did you cleaned the IACV, and air box ?.
Did you checked the fault codes ? for any sensor failure. if not check it first.



wajira
 
I have not checked those things. I will look into cleaning the IAC and I will research how to get the codes. I also noticed that there is what looks like a mechanical fuel pump on this engine besides the high pressure pump. Could this be bad? Also, I found through all the diagrams that there is a fuel pump filter. I have only ever changed out the low pressure and high pressure filters, but it looks like there is one more inline somewhere above the VST.
 
Send me an e-mail at [email protected] and I will send you the procedure for pulling fault codes and a PDF file showing what the codes mean.

If the mechanical (low pressure) fuel pump is going bad, if you rapidly squeeze the pump up bulb the problem will significantly abate.
 
Thanks wajira and CHawk, Ill send you an email soon. I took the dive into the motor today with my manual at hand. I cleaned the IAC valve screen which had some junk on it and I cleaned the Throttle body since I was there. The throttle body still has what appears to be rust deposits on the butterly flap. Not sure if that matters. It still opens and closes easily. I also removed the low pressure fuel pump. The manual says that if the plunger is "stiff" then replace the pump. I had to push with quite some effort to get the plunger to move. I'm not sure what is considered "stiff" in this case. Do you guys know how easily the plunger should move?
 
I replied to your e-mail this morning.

I doubt that the LP fuel pump is the issue, but it could be. There is a procedure for hooking up a fuel pressure gauge to the fuel pressure relief bolt. Skooter and several other folks have the specs on what the pressure should be. Memory says around 48 PSI, but not sure of that.


I do not know what "easily" means to them. But here is an old field-expedient auto trick. You can remove the pump, reattach the line coming in from the LP filter, hold it over a container, and manually operate the cam lever on the pump. A lot of fuel should pump out where the "out" line fits. That allows you to check for leaks and make sure the diaphragm is working correctly. BE VERY CAREFUL DONG THIS!
 
Since I have the motor torn apart, I went ahead and opened up the vst. Looked good inside and the float moved fine. I also tried the test that CHawk mentioned about the mechanical fuel pump. It seemed to pump a good amount of fuel I guess. Like I said before though the plunger takes effort to push in to pump that fuel out. I haven't done the codes yet because I assume everything has to be put back together before I turn the ignition on to get the codes?
 
I put the motor back together and checked for codes. No codes showed up. The MIL light came on and remained solid. I still have to check the fuel pressure once I get a gauge. The motor still revved up and down at idle. It almost sounds like the motor is going to die and then it revs up to keep itself going. It revs like this 3-4 times and then the motor runs somewhat smooth for approx. 30 seconds, then it goes back into the revving 3-4 times then smooth again. It continues this cycle. So, its not a constant revving up and down.

There was a point where the motor ran somewhat smooth for a couple minutes. During this time I noticed that the tach was all over the place. It would go from 800 rpm to 1200 rpm then to 1800 rpm then back down to 800 rpm. It was weird because when it was jumping around like that, the motor still sounded as if it was idling smooth at the same rpm. The tach was just doing its own thing.
 
Getting no codes is good.

Sticking with the LP fuel pump - good to know it is pumping and no leaks. However, only testing the fuel pressure will you know whether it is pumping adequately.

As for the tach, That is indeed strange. I'm out of my league on those. Hondadude is probably the most knowledgeable on tach's on this forum. However, that indicates a possible electrical problem or an ECU problem. I would check some connections, especially on the 26 pin harness connector from the ECU. Pin No. 1 is the logic ground pin. It's a green/black wire. Pin No. 10 is the tachometer wire. It is gray. If you have the Helm Shop Manual, see page 5-10. All of those pins should be sparkling clean.
 
Ok, If the fuel pressure is good then I can definitely rule out the LP fuel pump. In my head I am still questioning that thing. The tach thing threw me off too. I will check the pin connector. I had never noticed this before. I might just have to bite the bullet and take the boat in to a mechanic. Thanks for your help in all this.
 
Just noticed your thread and was wondering if you resolve this issue?

I had a similar issue same rpm range, there is a small mesh filter on the fuel rail that was dirty and causing fuel pressure to exceed 48psi. I measured it from 60 to 90psi. Once I cleaned it up the PSI was back to spec and the RPM wandering problem was fixed.
 
Seachaser,

For my benefit and others who wonder upon this thread, please describe just were that mesh filter is and how do you get to it. Thanks.
 
I finally received a new O2 sensor and I am literally installing it right now. I will let you know how this goes once I run the boat. Not sure when that will be as they are calling for rain for the next several days. The mesh filter on the fuel rail peaks my interest as well because I have never heard of it. When I originally brought the motor into the shop, they said my fuel pressure was a little low, but then they cleaned most of the typical fuel system items and the motor ran great. When I ran the boat, it ran great, but the alarm showed up. I will update as soon as possible because I hate it too when threads have no closure.
 
dagostino82 said:
I finally received a new O2 sensor and I am literally installing it right now. I will let you know how this goes once I run the boat. Not sure when that will be as they are calling for rain for the next several days. The mesh filter on the fuel rail peaks my interest as well because I have never heard of it. When I originally brought the motor into the shop, they said my fuel pressure was a little low, but then they cleaned most of the typical fuel system items and the motor ran great. When I ran the boat, it ran great, but the alarm showed up. I will update as soon as possible because I hate it too when threads have no closure.
Click to expand...

Check my thread: http://www.marineengine.com/boat-fo...utboard-225HP-Engine-Light-quot-ON-quot/page2

Entry #32

PS: I replied twice now, hopefully this one gets through. Said required moderator to approve.
 
Installed the new O2 sensor and no alarms showed up. Thank goodness. Original Low RPM surge is gone and now the alarm is gone. However, now I am noticing a new surge or some sort of RPM inconsistency. I noticed when I was cruisng around 4200rpm, the motor would shoot up to 5000 rpm for about 10 seconds or so then drop back down. It would wait a short while and do it again. Not sure if these RPM ranges are accurate because my tach wiring needs to be redone, but either way I can hear the RPMs change. Not sure what is going on, but I guess I'll start researching this now and maybe check that fuel regulator screen. Or just live with it until it gets worse!!!!!
 
No alarms or faults codes is good.

Your VTEC system kicks in at about 4500 rpm, so there COULD be a problem with your VTEC solenoid. Or it could be a problem with a clogged fuel screen under the HP fuel pump. But before going down that route, you said that your HP fuel filter had been recently changed. I would recheck that and make sure that the flimsy little O ring is properly installed, the spring behind the filter is properly in place, and the three bolts that hold the cover of the filter in place are tightened down properly. Have someone turn on the key switch for a few seconds while you observe the filter top to make sure that there are no leaks.

As you go in to check the HP fuel filter, you must remove the intake air control diaphragm for the intake air bypass control to get to the cover bolts on the HP fuel filter. You do this by unscrewing the two Phillips-head screws that hold the diaphragm in place. Once you detach the diaphragm, grab the arm coming out of it and pull it out as far as you can against the spring tension, then release it. It should pull out rather easily against the spring pressure and return quickly and smoothly. Then remove the vacuum hose going to the diaphragm, push in the arm into the diaphragm as far as it will go, put you finger over the opening where the vacuum hose goes, and see if it holds the arm in place. It should. (The arm will come out a little bit until enough vacuum has been created.) If either of these tests fail, then your problem may be due to a stuck intake air bypass baffles or a failed diaphragm. If so, send me an e-mail at [email protected] and I will return a write-up of how to diagnose and hopefully repair it.
 
Ah yes, I see it. I've "played" with this thing a few times when servicing the motor, but never really knew what it was or how it works. Thanks!!!!!!!
 
I checked the IAB and it appears to be functioning properly. Took the boat out again and low and behold the alarm sounded again. I was running the boat for a while both cruising and idling to catch bait. Cruised to my fist spot and the alarm sounded at idle. No alarms sounded on my fist trip out the other day and now this time it did. This can't be the new HO2 sensor again. Go home and it is the same code #1 which has the O2 sensor, low fuel pressure, bad coil and maybe one other thing it could be. Frustrated! Another symptom I have had which has happened only a handful of times since I have been getting these alarms. When starting the boat and getting on plane, as soon as I reach cruising speed, the motor starts "bucking" pretty violently actually jerking the boat. So, I come to a stop and let the boat idle a few seconds. The bucking stops and I go on my way. Can switching from ethanol to non-ethanol gas cause any problems? I'm starting to think that all my problems really got worse after I switch to non-ethanol. Just a coincidence right?
 
I can certainly understand being frustrated with this issue. It's a bit strange to me.

These engines are designed to burn either E-10 or non-ethanol 87 octane and up. I've never noticed a difference in performance.

One thing you have not posted is whether or not you have tested fuel pressure.

Let's go back to some basic diagnostics.

When you take out your boat the next time, try running it with the fuel tank filler cab off, or very loose. If no change, then you have eliminated a clogged vent tube to your fuel tank.

When the engine is acting up, check the primer bulb and make sure it is not partially collapsed. If not, you have eliminated a clogged or partially clogged pick up in the fuel tank and any restrictions in the fuel lines up to the primer bulb.

When the engine is acting up, pump the primer bulb rapidly. If that clears up the problem, then you're back to the low pressure fuel pump.

Try running your engine as you normally would with the cover off - it's possible that you have some restriction in the air flow entering the engine compartment or that you have an exhaust leak that is restricting oxygen flow to the intake.

Check where the fuel line enters the engine compartment and make sure it us not getting restricted when the engine is in different positions.

If none of that helps, hook up a 6 gallon or so external fuel tank and see if that helps. If not, then all issues in your fuel feed into the engine compartment have been fairly well eliminated.
 
Ok, I will have to start over from the beginning. I tried to test the fuel pressure a couple weeks ago, but my buddy's gauge did not fit the Honda. He thought they were universal fittings. Does Honda have a special fitting to test the fuel pressure? I also need to check the fuel pressure regulator screen like Seachaser mentioned.
 
Well, I am having a heck of a time trying to find a fuel pressure tester that fits this Honda. I've even searched for the Honda tester online. I rented a tester from Autozone but found that none of the adapters fit. Does anyone have an idea of what size I need? ---------- What I did find while attempting to check the pressure is that the vacuum tube going to my fuel pressure regulator was not connected. I am assuming that the shop that originally fixed the surge problem forgot to reattach this because they did say they tested the fuel pressure. Could this be my issue with the alarm? Could this cause any intermittent "bucking" of the motor? I still want to test my fuel pressure, but maybe this was the problem the whole time with the alarm. If so, I am excited and a little upset at the same time. The alarm didn't start coming on until after I brought the motor to the shop.
 
Yep - that vacuum hose is absolutely necessary to keep fuel pressure correct. So that was likely your problem.

Just where are you trying to test the fuel pressure? At the pressure relief bolt on the top of the HP fuel filter? That's a pretty standard 6 mm metric thread.
 
Ok, Thanks Chawk. Ill just put everything back together and test run some day soon. I am trying to test the pressure at the at that relief bolt on top of the HP fuel filter. For whatever reason though, neither my buddy's or the tester that I rented had the right fitting for it. I found the Honda one online for about $50 and will probably buy that one for future use.
 
Well, the motor ran great and no alarms yesterday. This whole time, it was because the shop forgot to put the vacuum hose back on the fuel pressure regulator. At least its fixed (hopefully). Thanks for all the help!!!!!!!!
 
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