08 BF225 fuel consumption WAY up

"On my last couple of trips my

"On my last couple of trips my fuel burn at cruise has gone way up.

Normally at 3800-4200 rpm's I burn approx. 8.5-12 gph's now its 12-16.5 gph's.

Now get this when you accelerate over 4500, gph's go DOWN even with Vtec kicking in.

The only time I ever burned over 16 gph's was 5200+ rpm's.

Yesterday i was cruising at 4800 rpm's at 14.5 gph's I reduced throttle to 4200 and gph dropped to 11,however, within 10 seconds, it shot up to 16.5 with no change to throttle or in hull speed. Increasing throttle past 4500 rpm's caused gph's to drop....WTF?

This is all measured on a Honda digital fuel gauge."

"Maybe a t-stat is stuck open.

"Maybe a t-stat is stuck open. This will tell the motor the engine is running cold, and thus send more gas to heat it up.

Also, maybe o2 sensor not working properly."

"Rick,
Thats what my mech sai

"Rick,
Thats what my mech said this am about the stat causing the engine to run cold at cruise.

Interestingly thermostats are not covered under warranty even though the engine has only 180 hrs.

Engine always flushed after use but never while running. Curious to see condition of t-stat.

I thought about the 02 also but I never got an alarm from the engine like other's have had w/ an 02 problem, besides i had the impression the 02 problems with the Honda's got resolved after the 05 model years?"

"O2 sensor failure due to wate

"O2 sensor failure due to water intake in exhaust pipes supposedly ended with SN 1500324 for the BAGJ model, and at SN 1500022 for the BAHJ model. However, O2 sensor can fail for other reasons.

Sounds like either a bad connection or a failing sensor. I'd first check for a dirty or corroded connection between the gauge and the ECM. Check all connections and clean - especially the one that connects the gauge package to the ECM.

If not, then it could be one of several issues with the programmed fuel injection or ECM. Did the MIL light come on while running? When you turn on the engine, does the MIL light come on and stay on, or blink? If so, you need to go through the ECM diagnostic procedure as outlined in the shop manual. Alternatively, have the dealer plug in the HDS and run through the diagnistics that way. That will pick up any problem with the sensors."

"WD,
We are going to hook it

"WD,
We are going to hook it up tomorrow to the HDS and see what the problem is.

I did have some steam at idle when I was at the ramp as if the engine was running too cool.

I have not had any lights turn on at idle or while running. However, 2 trips ago I did have an overheat alarm for a few seconds until i pulled back to idle, pisser was fine, never did see what caused it....maybe first sign of a stat problem?

Will post findings."

"Well here's the latest.

"Well here's the latest.

Mech pulled stats and says they look fine.
Ran diagnostics and all came back normal.
Ran boat in water to put engine under load and could not duplicate the problem(dont know if he even looked at fuel consumption, just ran engine hooked up to computer.)
Only thing he found was a slight spark misfire at the same rpm's i experienced the increased fuel burn.

Gonna pull the plugs tomorrow and see condition."

I think most of the 200's

I think most of the 200's and 225's will produce steam from the exhaust at idle or low speed. Mine certainly does.

Not unusual to have overheat alarm come on momentarily when decelerating from high speed. I think the owners manual even mentions that.

Technician should have checked fuel consumpion while running HDS. Ask.

The "slight misfire" in the 4000 - 4200 range sounds strange. Definitely pull and inspect plugs. Why not replace them in the process? Be sure to put anti-seize grease on threads either way.

Did you check & clean connections at gauge and at plug on engine?

"WD<

Thanks for your su

"WD<

Thanks for your suggestions.

Im assuming(and hope) he did check fuel burn while on HDS, thats what I took the motor in for.

I find it hard to believe that he did not find a fuel consumption problem after I confirmed it multiple times on my last trip.

Motor is an 08 w/170 hours and I have been anal with the maint. including use of corrosion block so I hope connections are clean and ok. However, abnormal GPH's occur at specific rpm and are not erratic at any other stage."

"Plugs pulled and carbon on th

"Plugs pulled and carbon on them, in fact alot of carbon for 170 hours.

Tech didnt like the fact they were Denso iridium plugs. He says Honda sometimes puts them in at the factory when NGK's not available, also says he has seen a few problems with the Denso plugs which were resolved by switching to NGK's.

Needless to say changed all plugs to NGK's. Will water test as soon as I have a chance.

Amount of carbon on plugs surprised me. I guess startron alone is not enough, maybe time to start ring free too."

"WOW - erratic fuel consumptio

"WOW - erratic fuel consumption at mid-range RPM's and high carbon on plugs - that sure sounds like a problem with your programmed fuel injection system or ECM (assuming fuel consumption gauge is accurate.) Changing the plugs may help, but I suspect that is just an indicator of the real problem. Seems like something should have shown up on the HDS. I'm stumped at this point."

"WD,
The tech's are stump

"WD,
The tech's are stumped also.
I get the sense that they are not too sure that its the plugs. Besides, like you stated, a plug problem would be the result of the true malfunction.
I wonder if the "Lean Burn Feedback Control" is acting up because that is the rpm range that the problem occurs, however, I would assume that any issue with sensor or the ECM would of shown up on the HDS.
The engine has run fine and this started acting up 2-3 hours ago. In fact, if I wouldnt of been paying attention tho the GPH's, I wouldnt of have noticed anything.
The only other sign was excessive soot around the exhaust which I assume would be a sign of running rich."

Update:
Ran with new plugs an

Update:
Ran with new plugs and no change.

Dealer put a call out to Honda Rep. who came down to see the engine.

Turns out it was the o2 sensor. Apparently I coated the sensor with Corossion Block when I sprayed the engine thus "plugging up" the small ports which read and monitor the outside air. HDS was not able to identify the O2 problem.

Honda took care of it under warranty.

So be careful when spraying the block down and avoid the sensor on the port side.

So

Gaffshot - Glad that you found

Gaffshot - Glad that you found the problem and it was an easy fix. I'm very surprised this didn't show up on the HDS. Sorta makes me concerned that the touted HDS system is not all it should be.