2003 yamaha 250 ox66

[PAULDIDIT]

I having problems with the engine running lean on the right bank and sneezing and stalling from time to time . sometimes I start it up and it runs perfect and smokes and runs like its suppose to and then other times I start it up and it runs like a bucket of bolts.Ive checked all the cleaned and checked all the grounds and inspected all the harness connectors for corrision. Do you possible think the stator or the pulse coil are starting to flake out ?
the other day we went to the beach and it ran perfect going over, and then 4-5 hours of sitting i started it up to come home and it was running really bad shacking, sneezing, and vibrating so I just shut it off and then restarted it and it was running fine again smooth.
what it was doing to me as well is that it use to fall flat on its face coming out of the marine after it had been running for 5 minutes , I would go get on a plan and running along at 4000RPMS for about a 1/4 mile out and then it would drop down to about 3000 RPMS and then come right back without me touching the throttle. I thought it was the fuel line restriction so I changed them all and it got better but not great. .

I would really appreciate any input that you could leaned

below is a list of what i have done to it so far

1) I have changed all 3 the lower pressure pumps with new ones and the mounting gkts. as well 2 where leaking
2) I've check the high pressure pump 36 psi idling and under load.
3) I've checked the tps voltage and its perfect and ranging good .
4) i've checked the O2 senser and thats ranging perfect. yesterday when it was running lean and sneezing i checked the o2 sensor voltage and it was at the bottom of the range and wouldn't come off so its diffenently lean . but whens its running good its ranging good
5) I removed had the injectors sent out cleaned and checked
6) I've checked for vacumum leaks and none could be found
7) the throttle body housing gaskets were replaced and are new
8) new NGK sparkplugs that the engine calls for
9) checked and cleaned the VST filter
10) replaced the fuel lines, primer bulb, fuel tank pick-up
11) All the filter are new and clean
12) checked the map sensor for being out of range good
13) etc.

[99yam40]

did you monitor the rail pressure when the problem shows up?
need to be looking at things when the problem is there

[PAULDIDIT]

i did have the fuel pressure gauges hooked up when its running like crap and the pressure hold strong . even under way the pressure never drops below 35 PSI the best that i can is running along at 25 MPH .

Its the crazest thing that sometimes that sucker will run sweet as can be and other time like a pale of crap. Like I said I left the beach the other day it started right up but was running like crap sneezing and running really rough the time it takes to pull the anchors and start idling out into the channel its still running like crap . then I pulled it back into neutral shout it off and restarted and it was back to normal running smooth and not missing or sneezing .

[scofflaw]

How bout winky blinky when this happens ? What's your rpm at WOT and how does it run then ?

[DennisG01]

I'm not a pro, so maybe someone with more experience can chime in and redirect if needed, but... I'd start by looking closer at something electrical. When you're "turning it off, then back on" and it "fixes" itself, that sounds much more like an electrical problem than a fuel problem. Fuel problems don't fix themselves that fast.

Something that sticks out is what you said about the O2 sensor. Remove it and clean it. If you're lucky, it will just be dirty and gunked up.

You didn't mention if the grounds you cleaned where only at the engine nor if you cleaned the positives leads? Look at the battery connections (physically remove) and the connections at the battery switch. Clean, inspect for corrosion underneath the sheathing, and replace. What type of battery voltage are you getting (with a meter) at the battery and at the engine?

[PAULDIDIT]

i don't have a winky blinky light but might have to invest in one .

She'll run 5500-5600 rpms and not miss a lick , actually she like that. never took at fuel reading at that rpm but didn't think i had to she wouldn't miss a lick and never bog down .

[scofflaw]

How bout your temp sensor, that controls open and closed loop.

I have some issues with my OX as well.

mind of its own 3k to 4k rpm's fluctuating . O2 sensor quits ranging at those rpm's. New O2 does same thing

No high idle when cold

Post back if you figure it out.....

[PAULDIDIT]

I have a high idle when its cold and idle down fine thats when it starts to sneeze and stall.

The o2 sensor was changed last year because of slow crossing over and ranging now it wwork perfectly .

but thanks for the inputs so fare , any positive info. is a plus with trying to track this down.

[boscoe99]

2) I've check the high pressure pump 36 psi idling and under load.

The fuel pressure should not be the same at different throttle positions with ********g engine loads. The fuel pressure will be lower at idle and higher as the throttle is advanced with the engine being loaded.

Check the pressure regulator for correct operation. While you are there inspect the strainer/filter between the regulator and the VST.

[rodbolt17]

if the regulator filter clogs it spikes rail pressure and runs rich.
I would monitor pulser coil outputs and the stbd bank charge coil outputs.

[99yam40]

that is interesting.
Rodbolt, how would pulser or charge coils cause the sneeze and stall?

[rodbolt17]

what creates the energy for spark on both banks?
what triggers spark AND injection?

[99yam40]

I did not think about the injectors not getting a signal to do their thing would cause a lean sneeze, thought it would be just a missfire.

Maybe not getting a full fuel charge, but still getting some of it

[PAULDIDIT]

update on the stalling and sneezing problems .

After rechecking all the sensors and switchs I bought a dva adaptor for my DVOM meter and checked the voltage coming out of the stator and pulse coil and the voltages on the stator were right on the money ,but the voltages coming out of the pulse coil were low and under yamaha specs. I removed the flywheel and inspected the wiring and coils and they looked visibly perfect .So I desided to buy a good used pulse coil from a guy that had one from a low hour motor that blew up and installed it. I'm happy to say its been running great sense .
Prior to buying the DCA adaptor I went out and bought a wink blinky light and it came back with no codes even when the engine was running rough and stalling. I would just like to thank rod bolt and the other guys for the info. into trying to solve this problem