VMAX 200 EFI OXY SENSOR

[<skeeter>]

I HAD TO REPLACE MY OXYGEN SENSOR LAST YEAR BECAUSE IT WAS CONTAMINATED WITH CARBON. I HAVE USED YAMAHA RING FREE EVER SINCE BUT TONIGHT I TOOK OUT THE O2 SENSOR TO CHECK IT BECAUSE IT WAS RUNNING ROUGH AND IT WAS ALL CARBONED UP AGAIN. I CLEANED IT AND THE HOUSING AND TUBE BUT HAVE NOT RAN IT YET TO SEE IF IT WORKS. DOES ANYONE HAVE ANY IDEAS WHAT I CAN DO TO PREVENT THIS? IS ANY ONE ELSE HAVING PROBLEMS WITH THEIRS? MOTOR IS A 1999 VMAX 200 EFI. THANKS

[<boats.net>]

You might take to your dealer and let them check oil injection and fuel system to see if running rich

[<skeeter>]

I did that last year and he reset the oil control rod and checked the fuel system and replaced the o2 sensor. I'm just looking for other ideas and opinions and to see if anyone else was experiencing this. Thanks

[<Ed McKenna>]

Other than visual inspection of the sensor are you having any other issue with engine performance/idling/higher than normal RPMs? It should be cleaned every 100 hours or so as a general rule. How much use are you giving it?

Stuck open thermostats can cause more fuel to be sent to the pistons and affect the O2 sensor. Likewise there is a purge valve at the base at the rear of my Yam 250 EFI. I had to clean a bunch of salt build up out of that. It was causing the purge valve to stick open slightly, and hence was letting water flow when it shouldn't. Cleaning that had a huge effect on performance. The purge valve is just a spring loaded piece of plastic that pushes against a rubber housing to seal water flow.

Ed

[<skeeter>]

Thanks for the info Ed. I will check that out . The motor was idling rough, wouldn't start instantly like normal sometimes had to hold the pedal (hotfoot) down a little to get it going, sluggish holeshot, and I would be going along at 5500 rpm and it would drop to 5000 and I could let off and hit it again and it would pick up and run good for a little bit then drop off again. All this is gone after I cleaned the O2 sensor and it seems to be running pretty good. Another question for you, every time I start it after its warm I get a big puff of smoke then its clear, it's been this way since it was new and others seem to do the same is this normal? I run quite a bit doing tournaments but not usually long distances (2 to 15 miles generally)Thanks

[<Ed McKenna>]

Good to know your O2 issue resolved it. This stuff is a pain in the ass to deal with, when all ya wanna do is just fish!

Regarding the puff, mine was doing it this week also until I replaced one of my low pressure fuel pumps see post from last night to someone else. I haven't had it happen since but also haven't given it a hell of a lot of use.

I do lots of off shore giant blue fin tuna fishing 25-35 miles off shore so reliability is pretty important.

One thing that is a fairly simple test is to measure the voltage of your throttle position sensor. Mine is supposed to be .5 volts plus or minus .02. Look on the Yam specs page to see where it is if you don't know what I'm talking about. My Yam dealer loaned me a wire splice that plugged in. Then using a volt meter you take a reading. The reading should only be off by .02 + or -. I recommend looking at this because from your info it's not clear who if anyone has ****ed around with your idle screw or your throttle position sensor. Increasing idle will affect the reading on the sensor.

This sensor basically adjusts the flow of fuel when you quickly go from fast to slow. It prevents the engine from getting starved or over fueled. This may be slightly out of spec and causing the puff. Its adjusted by losening the screws SLIGHTLY on the side and SLIGHTLY moving up or down, then retighten. Getting it within spec when engine running at 700 RPM is like threading a needle with your feet. [img]smile.gif[/img]

I had brought mine to a mechanic (non dealer) who frigged with mine, and never put it into spec.

You can either borrow the wire splice, buy one, or make one. I've since made one out of 3 strands of wire that I can jury rig to get the same result. Hey I'm a yankee from maine pennies add up with this stuff [img]smile.gif[/img]

Not sure what else for you to review other than plugs. Make sure they aren't built up with carbon. Given that your 02 was dirty, chances are that the plugs are also.

You should run a shit load of "Ring Free" through the tank. See the back of the bottle for what a shock treatment is. I think it's 2oz per gallon of gas. Most cost effective to treat when your tank is near empty. This will clean up your pistons, rings and cylinder heads. I HIGHLY recommend doing this. Then use ring free as part of your routine maintenance with every tank full I think 1 oz per 10 gallons.

This past week I replaced my head gasket and as such had a look at my piston heads. They definitely had some carbon build up on them, and I do use it pretty regularly. But have never shocked it. Mine built up I'm sure when my 02 sensor was clogged - too much fuel being delivered.

Good luck, Ed

[<Hamfisted>]

I use to use RingFree all the time and had the same carbon buildup as if I didn't use it at all. A friend of mine recommended switching to SeaFoam instead of RingFree and I've been carbon free ever since. It seems much more effective than RingFree. You can find SeaFoam at most NAPA stores as well as CarQuest and Northern Tools stores for about $5 a can. To do a shock treatment just empty out your Racor fuel filter and refill it with straight SeaFoam and run the motor on the garden hose at idle for 10 minutes then shut it off for 30 minutes then run it for another 10 minutes or until it stops smoking like a mesquito fogger. If you have a carbon buildup you may likely see chunks dropping out of the prop exhaust so don't be alarmed. After that you should just use it in the gas tank as a fuel stabilizer to keep carbon off.


Mike ........ Miami, FL

[<seahorse>]

For info on how the O2 sensor works and how to clean and test it, go to:

http://www.thebassguide.com/home/News/05-30-2002-01.htm

[<fisheye>]

The link posted above has been removed/blocked..

What do you use to clean the sensor? I have about 550 hours on my 250's and need to clean one of them. I get the same symptoms as posted above. A loss of rpms at WOT. I would like to try cleaning instead of replacing if possible.

[<jb123>]

soak the lower half of the sensor in carb cleaner overnight...not above the threads....it can also be lightly heated up with propane torch...put the heat to it no more than a second at a time.that is how techs test them...with a volt meter and a torch....watching the high to low temp variance.