BF75 Running Rough and Surging

Hello all,

could you please give advice on my 2011 Injected Honda.

It runs fairly rough through most of the rev range and also at hunts or surges between 1800 and 2200 RPM. Acceleration is fine and fuel consumption seem OK.

It has new fuel pump and filters.
Ive had it to the Honda dealership who have done all the standard checks and valve clearances. they had no clue except "Just use it alot and it might go away".

Thanks in advance.

Some of the early models had ECU issues that caused erratic rpms. Depends on the serial number.

Post your frame serial number and I will check to see if that may be a possiblity.

What compression and/or leakdown test results did the dealer have?

I have had a couple come in that got had thermostats that were stuck open and the compression was affected by the carbon buildup. A good decarb job and both thermostats changed, fixed the compression and the running problem.

If dealer did not know the answer to the problem, did they contact their District Service Manager for help?

In any case, if you still do not get satisfaction, call Honda customer service and discuss it with them. That will help stir the pot. If you are in the USA, the number is 770-497-6400.

Mike

Hello Mike,
the engine has new thermostats.
I dont have any further info on the compression figures, the invoice just says "OK".

I did however find a wire with a damaged insulation and 2-3 broken strands just before it goes into the Oxygen Sensor plug (engine loom side). I intend to repair the wire by installing a new waterproof plug. Is this something which could cause the problem?

As for contacting the Honda Management, no I havent. The dealership is the only one in my state (remote northern Australia). It is 2400 kms to the nearest other one, so I dont really want to go peeving them off by complaining. Customer service is a strange concept in this part of the world.

Thanks

Daryl

I understand the reluctance to escalate the issue...

The leads on the o2 sensor might cause the problem, but I doubt it. I hope I am wrong.
If the o2 sensor is out of range, it normally causes a check engine light to come on and gives an audible alarm.

A bunch more questions.....

-Have you had this motor since it was new?
-Did this start all of a sudden or did it come on a little over time?
-When you check oil, is it a little below the full mark....like it should be?
-What spark plugs are in the motor? Denso's or NGK? If Denso's, change the spark plugs to NGK IZFR6K-11E (and only this number plug...no equivalents). They are not cheap, but they are a much better plug. The plugs may look perfect, but misfire.
-Post that frame serial number....just to check if that series has any known issues.

Mike

G'Day Mike,

some answers for you.

-Have you had this motor since it was new? No, I bought it around 6 months but havent used it much.

-Did this start all of a sudden or did it come on a little over time? It seemed to occur after I began getting and alarm which was for NO2 sensor, part of the fault finding was to test the fuel pressure regulator, which failed its check (no fuel at all came out of the discharge pipe). After the regulator was changed, the alarm went away, however it now runs rough, bad idle/hunting etc.. The dealership have tested the fuel pressure however and its good.

-When you check oil, is it a little below the full mark....like it should be? I checked the oil level and to my horror, the level was way too high!! I removed around 1.5L to get it back down just below the full mark. Pretty dissapointed in myself for not picking this up without you prompting. I ran the engine and its still the same though

-What spark plugs are in the motor? Denso's or NGK? If Denso's, change the spark plugs to NGK IZFR6K-11E (and only this number plug...no equivalents). They are not cheap, but they are a much better plug. The plugs may look perfect, but misfire. Plugs are the correct NGK Iridium plugs exactly the same part number as you quoted, they are nearly new (and yes they are expensive).

Engine Frame No. is BBAJ-1006567

When I had it at the dealership, they also checked each injector by removing each one sequentially with a known good injector and no change. They noted there were no fault codes.

Thanks for you ongoing help.

Daryl

Take a look at the spark plugs. I would be very surprised if they did not have carbon buildup due to too much oil.

Since we do not know how long it has been this way, your rings may have gotten carbon buildup also. Although, dealer said that the compression was good. If it were suspect, they would have performed a leakdown test to zero in on the problem. They did find the issue with your O2 sensor, so, it sounds like they do know what they are doing.

It probably is impossible to know for sure why the oil was too high.....just put too much in or engine running rich and fuel is getting past the cylinders and going into the crankcase.

Do you do a lot of idling? If you do, it is possible that is what caused the oil level increase. Usually, here in the US, it is coupled with operating in cold water. So the motor never really gets to temperature and the fuel never completely burns at idle. There is a Service Bulletin from American Honda that changes the head gasket and thermostat (to a higher temperature) to help resolve the problem.

Your motor serial number falls in the series potentially affected by this problem. There is a questionaire that the customer fills out that includes a log of the oil height over time.

At this time, I would just check the oil before you go out to use the boat. Try to do it with the engine at the same tilt angle etc, for consistency, and record any difference with how many hours of use.

I do not know what type of decarbination products you have in Australia. You may want to check with your dealer. I would recommend a good decarbination job to get rid of any potential carbon buildup...
Yamaha Ring Free is a miracle worker, if you can find a Yamaha dealer.

Mike

Ok so I checked the lower plugs and they both are very black and appear "greasy" which I would imagine is attributable to the oil.
Their is alot of staining of the ceramic insulator and centre electrode. The plugs were replaced 11hrs ago.

I would imagine they should be a greyish white colour??

I am going to try get hold of the Ring Free as I think you could be on the right path with a decarbonisation, although I think it will need to be shock treated to remove deposits.

The engine has 1130hrs on it, so if it hasnt been done before and the fuel quality is poor, the head/valves will be caked with carbon.
It has new pistons and ring's in it which I installed 11hrs ago.

Daryl

I agree on the shock treatment. Hopefully, you have a 3 gallon tank. Drain your vapor separator before you begin the process, so you do not have to burn through the gas before you actually "treat" the engine.

It sounds like you know what you are doing if you replaced the pistons and rings. Since that was an unknown before....have you double checked to be sure that the timing marks are still lined up. If the chain is off just one notch, it can cause all kinds of unusual things.
Normally, the chain will not jump time unless the tensioner had an issue or if the cam chain guides deteriorate.

For others reading this....the chain, tensioner, etc are totally enclosed and bathed in oil....so it is very unlikely that a critter built a nest...as happens a lot with engines with exposed timing "belts".

Back to your decarb....

The way I do it...since we do not have direct access to water (it is just up the street, though)....After draining the vapor separator, I run the engine on the decarb tank for about 20 minutes at a fast idle, on a hose. Then I let it sit for an hour or so. After sitting, I run the engine a little faster for the first few minutes, then, I repeat the process about three more times. If I have originally found a problem with the compression, I repeat the compression test on the problem cylinder or two about 1/2 way through the process to see if it is doing any good.

Once I do that process, I take it to the water and back it in and run up the rpms in gear, on the trailer, up to mid range. I want to be sure it gets well up to temperature to burn the crap out.

Finally, one more compression test...sometimes even a leakdown test....again...depending on what problem I was trying to fix.

All that being said....if you have access to water, all the steps would be better in the water under load. Of course, you have to sit and wait for an hour or two or more between steps to let the solution do its work.

Be sure to change the oil after all is finished.

I would change the spark plugs, but in your case, you may be able to put them in some solution to clean them up. You certainly should not use a mechanical cleaning process or you may ruin the plugs for sure.

Mike

I checked the cam chain marks when I re-checked valve clearances.

I will try the cleaning of the plugs and decarbing, although it is 300klms (or 190 Miles) to my nearest water, so it will be in the next few weeks.

A little more history on the engine.

I bought it second hand (very cheap), and was seized as it had shut down after having water contamination of the fuel system.

-All new fuel components, HP and LP pumps, filters, float needles, injectors. (except for pressure regulator)
-All new pistons, rings, bearings and piston pins. I checked the conrods and they werent bent from a potential hydraulic. I had the cylinder's honed and tested for bore size and still in spec's. It appears that the engine stopped from water in fuel and after it sat idle for a month before I bought it, the rings corroded to the cylinder walls and appeared seized.
-New thermostats
-New NO2 sensor
-New spark Plugs
-Didnt touch the head or electronics.

After I reassembled everything I filled it with oil (I thought I had it just on the full mark???), and kicked it over.

It seemed to run fine but after about 20 secs it would bring on an alarm with a code (I jumpered the test plug) for NO2 sensor.
The manual said to test the fuel pressure regulator (the one item I didnt change) and whereas it was supposed to discharge a certain amount of CC of fuel from the disconnected pipe, nothing came out. I replaced it and although it stopped the alarm and codes, around that time (I dont think it happened exactly then) but it began to intermittently rough and have an erratic idle (randomly sits between 660 and 800, and drops again when put into gear)

Progressively the roughness got worse. It seems as though a cylinder isnt firing every 2-3 seconds, it isnt rythmic, its quite random.

Another symptom is that if I set around 2000RPM, it will rythmically hunt by +/-200, now this isnt random at all and is quite predictable about every 5 secs.

The engine seems to have plenty of power and torque and fuel flow/economy is good, although I havent got anything to compare it to. I believe I have the boat well propped and at around 4800 RPM (cruising I have around 22-23 L/Hr).

Sorry for the long story but hope this sheds more light on my dilemma.

Regards

Daryl

Hondadude, any ideas mate??

Some further info is that when it was bringing on alarms for NO2 sensor, it was running fine. But after I changed the fuel regulator, it now runs rough, but doesn't have an alarm????

UPDATE!!!!

Ive isolated the source of the problem...However Im not sure why its doing what it is...

When i either disconnect and blank off, or alternately if i pinch with a set of pliers, the discharge tube which runs from the Fuel pressure regulator (FPR) back into the vapour separator, the engine instantly idles and runs smoothly, although it will eventually bring on an alarm.

So noting that Ive replaced the FPR already (and Im human so could have stuffed it up), why is this happening?
I did the test described in the factory manual whereby you disconnect the discharge hose and run the pump for 2 secs (turn on the key) and measure how much comes out. In my case I get 50ml of fluid which is 1.6 oz. The book says you should get at least 0.7 oz or more. Is this excessive?

The FPR has a pressure bellows which connects to a vaccuum port on the throttle intake, i wonder is the bellows diaphragm stuffed?
Im reluctant to replace this item again, but it wouldnt be the first time a new item stuffed out.

Any help or tips appreciated.

Have you checked your fuel pressure? Pinching off the line should raise the fuel pressure.

When the alarm goes off....what alarm are you getting? Maybe....o2 sensor?

I am not sure what else would cause the alarm.

Since you decarbed, you might want to check the high pressure filter again, just to be sure that it was not affected by the solution and lowering the fuel pressure.

Also, squeeze the fuel bulb to be sure that the vapor separator is being filled by the low pressure fuel pump.

No easy answer from me at this point.

Mike

Thanks Mike,
yes it is O2 sensor alarm. When I dont pinch the line, it doesnt come on.

I have all the gear to decarb, but havent been on the water yet to do so.

My fuel bulb is fairly squishy..i.e I cant ever get it to go hard. Also I notice that when the engine is running, the LP Fuel filter is only ever about 1/4 full.. is that correct?
Thanks again for the reply.

Daryl

If the bulb never gets hard, then the bulb could be bad; there could be a leak ; or the needle in the vapor separator is stuck open. Normally the fuel filter should stay pretty full. It should at least be full when the bulb gets hard. There was an issue with the fuel pump in earlier models, but the fuel starvation was at high speeds and high loads.

When you squeeze the bulb hold it with the arrow pointing up. The check balls work better that way.

Mike

Problem solved. It was a defective Fuel Injector (I bought a set from an outboard wreckers... my mistake!!!). The mechanics who looked at it originally used a "Known good" injector to swap them out individually. Turns out this method didnt diagnose the problem, full bench flow testing revealed a bad spray pattern and low flow from one of them.

Glad to have it back and running smooth.