Yamaha 115 4 stroke sputter/stalling. Help!

[Markdelz76]

Ok so update. Replaced injectors and spark plugs. Put fuel pressure gauges on fuel rail and read 37 psi when running. Put fuel pressure gauge after low pressure fuel pump and read 10-11 psi when running. It is still stalling. Right before it stalls the gauges stay about the same, maybe go down a few psi. The idle air control valve clicks when I start and then turn off the motor. If the motor stalls, I do not hear the valve click. When it gets ready to stall, I hear it almost gasping for air, like an inhaling for air sound. Ughhhh

 

[Fishtales]

Maybe try SIM Yamaha.

 

[seasick]

Ok so update. Replaced injectors and spark plugs. Put fuel pressure gauges on fuel rail and read 37 psi when running. Put fuel pressure gauge after low pressure fuel pump and read 10-11 psi when running. It is still stalling. Right before it stalls the gauges stay about the same, maybe go down a few psi. The idle air control valve clicks when I start and then turn off the motor. If the motor stalls, I do not hear the valve click. When it gets ready to stall, I hear it almost gasping for air, like an inhaling for air sound. Ughhhh

Please clear up my confusion. Does the motor shudder and stall when the control is in the idle position or does it act up when revs drop to about 2000.
If it acts up at idle, does moving the throttle lever up reduce or stop the shudder and stalling.?
I can understand that the low pressure would drop as revs lower. That is probably not an issue but the high pressure should be pretty constant. Does that drop also?
When you hear the motor gasping what revs does the tach display?
Why did you replace the injectors? If I were going to replace anything, it would be the IAC valve assuming that the stalling symptoms occur when revs get to idle speed and not necessarily when crossing the 2000 rev range

 

[Markdelz76]

Please clear up my confusion. Does the motor shudder and stall when the control is in the idle position or does it act up when revs drop to about 2000.
If it acts up at idle, does moving the throttle lever up reduce or stop the shudder and stalling.?
I can understand that the low pressure would drop as revs lower. That is probably not an issue but the high pressure should be pretty constant. Does that drop also?
When you hear the motor gasping what revs does the tach display?
Why did you replace the injectors? If I were going to replace anything, it would be the IAC valve assuming that the stalling symptoms occur when revs get to idle speed and not necessarily when crossing the 2000 rev range

The motor shudders and stalls when it is in idle position. When it acts up, moving the throttle does not fix it. But last time it was in the water, I plowed back to the marina around 2-2500 rpm
And it did not stall or shudder. It was only a quick ride though, about 2 football fields. Right when I pulled back to around idle rpm, it stalled.
I replaced injectors because years ago I bought non OEM ones and just did it for piece of mind. I did not go above 2000 rpm yesterday because I was on a work rack at the marina. But I did go to 1200 and it started shuddering. I am wondering if it is the IAC valve as well. But I did hear it click if I was to start and then shut off the motor with the key. I did not hear it click if it stalled. The high pressure did drop a couple psi as it was stalling. When the motor is gasping the rpm tach is dipping pretty low, tries to come back up, and stalls

 

[seasick]

When the revs go a tad below the spec idle revs, the motors can sputter and what I call sneeze. So the sputter is not necessarily the issue but rather why the low revs? That could be fuel or air in your case.
I searched for F115 stalls issues and found several folks who said that the IAC is the culprit but there was one interesting post about a torn diaphragm in the low pressure pump, The clue was that the motor was making oil, that is to say that the oil level over time got higher. The leaky diaphragm in the low pressure pump allowed gas to bleed into the crankcase. So check your oil level to see if it is higher than it should be.

Regarding the IAC, clicking means the valve is getting power/activated but it doesn't necessarily mean the valve is working correctly

 

[Markdelz76]

When the revs go a tad below the spec idle revs, the motors can sputter and what I call sneeze. So the sputter is not necessarily the issue but rather why the low revs? That could be fuel or air in your case.
I searched for F115 stalls issues and found several folks who said that the IAC is the culprit but there was one interesting post about a torn diaphragm in the low pressure pump, The clue was that the motor was making oil, that is to say that the oil level over time got higher. The leaky diaphragm in the low pressure pump allowed gas to bleed into the crankcase. So check your oil level to see if it is higher than it should be.

Regarding the IAC, clicking means the valve is getting power/activated but it doesn't necessarily mean the valve is working correctly

Thanks for your help man! I ordered a new IAC and will update after that. I also will check the oil for any gas in it. My fuel pressure regulator is pretty rusty too, so thinking I am going to replace that as well

 

[seasick]

One thing at a time.. If you start bulk replacing parts and there is a problem, you may not know what caused it. Sometimes the new parts are bad.

 

[Markdelz76]

Well, replaced the IAC and it ran fine for 10 minutes on the muffs and then died out. The IAC is pretty hot to the touch. Any other ideas?

 

[seasick]

Ran for ten minutes at idle speed? Did it gradually slow down or did it just sneeze and die. When it dies can you immediately restart the motor or is it harder to start.
Run your test again, You need to know if the IAC valve got fried for whatever reason . Since the motor idles for 10 minutes, obviously the IAC was working.

You may need to get a diagnostic terminal connected to see if there are any clues to what is going on

 

[Markdelz76]

Ran for ten minutes at idle speed? Did it gradually slow down or did it just sneeze and die. When it dies can you immediately restart the motor or is it harder to start.
Run your test again, You need to know if the IAC valve got fried for whatever reason . Since the motor idles for 10 minutes, obviously the IAC was working.

You may need to get a diagnostic terminal connected to see if there are any clues to what is going on

I wish I could use a diagnostic terminal but it’s a 2000 so I can’t hook a computer up to it. Ran for 10min at idle speed. I can start it back up then it dies faster. I am going to replace the thermostat and see what happens. If that isnt it, I may need to hire a mechanic. Not sure what else it could be.

 

[seasick]

I highly doubt that the t-stat has anything to do with the stalling.

 

[seasick]

take a look at this posting

Yamaha computer fault codes and readout (2002 f115 EFI) - Yamaha Outboard Parts Forum

Ask the experts on our Yamaha Outboard Forum for repair issues, diagnosing problems, links to diagrams, suggestions on buying parts and more. They can answer questions for any Yamaha outboard model or horsepower.

www.yamahaoutboardparts.com

 

[Markdelz76]

take a look at this posting

Yamaha computer fault codes and readout (2002 f115 EFI) - Yamaha Outboard Parts Forum

Ask the experts on our Yamaha Outboard Forum for repair issues, diagnosing problems, links to diagrams, suggestions on buying parts and more. They can answer questions for any Yamaha outboard model or horsepower.

www.yamahaoutboardparts.com

I saw this on a post -
Here was Rodbolts advice on that thread...


here's what creates the 700 RPM or so idle. mostly its by the temp sensor, TPS and ISC.


its possible the t-stat is stuck its possible the ISC is sticking or dirty and its possible the TPS voltage is incorrect. the ECU will adjust air, via the ISC and ign timing based on signals from the ECT and TPS to try to maintain the ECU mappea idle speed for the throttle angle and engine temp inputs. now ya just gotta find out whats not quite right. remember the ECU is rather stupid.

 

[seasick]

The engine temp is used for the most part to adjust the air/fuel ration richer for a cold motor. I think that a stuck open t-stat would cause the motor to add choke ( more gas). On this post, the motor is slowing down.
I see how the TPS could ne an issue but it would have to be something heat related since it takes a while for the motor to act up. TPS sensors that act up when warm are a common oroblems on some older Mercs but I am not aware of similar issues on Yamis.

Here is another thread on similar stalling issues. Read all the way to the end.

ISC valve replace? - Yamaha Outboard Parts Forum

Ask the experts on our Yamaha Outboard Forum for repair issues, diagnosing problems, links to diagrams, suggestions on buying parts and more. They can answer questions for any Yamaha outboard model or horsepower.

yamahaoutboardparts.com

Was the valve you bought a Yamaha OEM part?

 

[Fishtales]

Time for a mechanic.

 

[seasick]

a real mechanic

 

[Markdelz76]

Got a certified Yamaha mechanic and still stumped. So far replaced low pressure fuel pump, high pressure fuel pump with VST, thermostat, VST and ran off an external tank. It runs better than when I originally posted this, but it still sputters (doesn’t stall anymore). Waiting for the mechanic to get back from a trip. But any other ideas?

 

[seasick]

get another mechanic. The replace everything one at a time is poor practice assuming you paid for all those parts. The VST pump is an expensive part. Measuring the fuel rail pressure would have been a better approach. I may have asked this before but I don't remember.
Does the idle slow down and then the motor sputters and dies (or just sputters). If the idle is too low, these motors will sputter and stall.
When the motor sputters, use the shift override button on the control and raise the revs if you can. If you can let the motor run for a while to warm up. Put things (shift) back to normal and see how the motor runs

 

[Markdelz76]

get another mechanic. The replace everything one at a time is poor practice assuming you paid for all those parts. The VST pump is an expensive part. Measuring the fuel rail pressure would have been a better approach. I may have asked this before but I don't remember.
Does the idle slow down and then the motor sputters and dies (or just sputters). If the idle is too low, these motors will sputter and stall.
When the motor sputters, use the shift override button on the control and raise the revs if you can. If you can let the motor run for a while to warm up. Put things (shift) back to normal and see how the motor runs

We hooked up a fuel pressure gauge at the rail when it was sputtering and it was dropping pressure therefore assumed it was the HPFP. The LPFP was also leaking gas into the oil, so I do believe it is a combo issue here. My thermostat was definitely bad as well. I am going to look into another mechanic though

before replacing all these parts the motor would sputter and stall. Now it sputters and will run when given gas. But when I was pulling into the slip, it did stall.

 

[efx]

I had the same engine on a mako 17. It was at the age that you had to chase and follow the entire fuel system from tank to fuel rail. Mine would also sputter and stall at idle. What I found out was the fuel cup had an overtighten nut and a crack in its cap allowing air in. Replace the cup and cap. It’s greenish versus yellow. That was first. Then I found the high pressure fuel pump filter screen was easily clogged even after cleaning. Get a new one. Then I replaced all injectors. They must seated evenly when pushed into the block. Also unclip every sensor ant top of engine and clean the contacts then re attach. Plugs also, must be tight. Make sure all small hoses are not cracked. See photos of how far you have to go.

good luck. It’s tough.