BF225 idling issues

Hi
I have a 2014 BF225 and after it completes its fast idle, the motor begins to hunt / shutter .
On cold start at times , and when putting into gear first thing in the morning the motor surges and will stall.
Runs well above idle and all the way to WOT. But will hunt at idle , can feel it throughout the boat.
Below is the list of things that i have completed and still am having issues .
Replaced H02 sensor
Checked IAB coil resistance , 42ohms , ok.
Swapped IAC valve with a known good one.
replaced Fuel regulator.
Inspected screen on fuel injection rail and cleaned.
Inspected VST and HP fuel pump , all ok, screen clean on HP fuel pump. Float in VST ok .
Check valve proven from vacuum tank.
Performed fuel pressure check and fuel pressure good at 45PSI
HP fuel filter replaced, LP screen checked and replaced.
Checked all vacuum hoses for leaks and blockages, all ok.
Did find that the vent line off the VST to atmosphere was partially blocked, cleaned and is ok.

Pretty well stumped, the engine has 1050hrs on it .

Any help appreciated.
Cheers
Rob

Did you try to pull fault codes?

First thing that comes to mind is that possibly the low pressure fuel pump is acting up - worn plunger or leaking diaphragm. At initial start when problem starts to happen, have someone rapidly pump the primer bulb. If that cleans it up, replace the pump.

Also, when problem happens, check the fuel level in the low pressure fuel filter site bowl. It should be around 1/2 full +/-.

Hi CHawk
No alarm codes at all , but on the smart gauge i do have a flashing spanner, so i may have some fault codes. Last time it was serviced by a marine technician, he could not communicate with the computer , so we could not get a diagnostic read out.
Is there a way to pull the fault codes , i have simulated alarms and have reset them via shorting the test plug cores and depressing the kill switch 5 times. Initially MIL was not functioning so swapped with battery LED and was able to see codes when simulating O2 sensor and MAP sensor.

Have tried to squeeze bowl whilst the motor is hunting and it hasn't made a difference, may remove fuel ump and inspect the plunger and diaphragm.
Thanks for your help

Rob

The procedure for pulling codes is here: View attachment Procedure for Getting Fault Codes.pdf

What the codes mean is here: View attachment MIL Fault Codes Scanned.pdf

Single most common cause for your idle surge is valve clearance. Disregard the manual and set the inlets at .010" and exhaust .012" . Try it.

Hi Fellas
Thanks again for your help, no fault codes present at all.
Haven't had the chance to check the valve clearance yet as i have to go to work for 6 weeks due to modified roster , but will have a good look at them when i get back.
The LP fuel pump plunger was tight / stiff to push in, is this normal.
Have noticed that the fuel level in the LP fuel filter bowl is full , does that indicate poor pump performance ?
Thanks
Rob

I can assure you the valve clearance will fix it if you adjust to the values I gave you. If there was a fuel issue it would more likely cause issues at high demand,ie mid to full throttle. And to answer your question, yes the pluger should be hard to push in, they have quite a heavy spring.

Hi Fellas
iang6766 , was given extra day off so checked and adjusted valve clearances to the figures you gave me , as found they were all over the shop cylinders 3 and 6 were the closest. Ran up engine and it runs perfect thanks a heap mate , it hasnt run this good for a long time. Really appreciate it.
Chawk , thanks for all your help as well , this is an excellent site with a wealth of knowledge.
Cheers
Rob

You are most welcome, happy to help. It will be interesting to note a lot of V6's out there have lumpy idle, a lot of owners just accept it.

Rob s said:

Hi Fellas
iang6766 , was given extra day off so checked and adjusted valve clearances to the figures you gave me , as found they were all over the shop cylinders 3 and 6 were the closest. Ran up engine and it runs perfect thanks a heap mate , it hasnt run this good for a long time. Really appreciate it.
Chawk , thanks for all your help as well , this is an excellent site with a wealth of knowledge.
Cheers
Rob

Click to expand...

Hi Rob, glad to hear you solved the idling issue.
Just out of interested what were the clearances before you adjusted them to what iang6767 recommended which is on the tighter side to what the honda manual suggested.
Just for a bit of further information I've had mine set to standard values on a service interval of 1000 hours(engine is at 3000 hours )
With no running issue except out of the water when you run it on the muffs it a bit lumpy but I suspect that was lack of exhaust back pressure , and runs fine in the water.

Just for the record I recommend the inlets slightly looser 010 as opposed to 008 and ex 012 as per manual. We have found the AK1 and on for some reason idle a lot better better with the extra 002 for the inlet valves

iang6766 said:

Just for the record I recommend the inlets slightly looser 010 as opposed to 008 and ex 012 as per manual. We have found the AK1 and on for some reason idle a lot better better with the extra 002 for the inlet valves

Click to expand...

You are right , being in Australia I work in millimeters and did a quick conversion in my head before posting and was off a bit, forgot to carry the one or something like that

Hi Ozzie
Inlet valve clearances were a bit out, between .008 and 0.010" , but the exhaust valves were miles out, couldnt even fit an 8 thou feeler gauge between the clearances(or lack of clearance). Have been out a few times prior to being put into quarantine for work and motor runs like a dream , idles on muffs with no issues , definately better fuel economy as well and a bit more poke.
Cheers

Hmmmm - I highly recommend that you NOT run this engine on muffs UNLESS you have exceptionally high water pressure available. They will quickly overheat. That's been my experience.

Bill, I flush my BF200 on muffs no problem and my water pressure at home is below average. Not sure what muffs you use but I find if I bend the ears together before each use so they are nice and tight , then it works fine

Roger that. I've tried the rectangular dual-feed muffs (which are terrible) and several of the round ones with a single side feed, and invariably get an overheat alarm. Water source is a 5/8" hose connected to a 3/4" faucet fed by a home well pump. Anyway, I've resigned myself to using a large, oversize trash can elevated by several pallets.

It may be that I just don't have sufficient pressure from the well's holding tank. Guess I can check that, recharge the tank, and set the pressure level higher.