Temp sensor and thermostat issue

[jackmanjls]

Last year I had trouble with my F90TLR running rough on fast idle and then stalling when put into neutral (termed: the "issue").

After doing some analysis I found that cleaning the temp sensor and thermostat resolved the issue. The motor ran fine (Oct to May) all last winter in fla. I stored the boat for the summer (in Fla). I came back this Oct and when starting the motor in the driveway before launching with muffs it ran fine. I took to the landing and once in the water it exhibited the same symptoms as the "issue". I put the boat back on the trailer.

I then bought/installed a new temp sensor and cleaned the thermostat. I relaunched and the motor ran fine for 1 outing.

Yesterday, I started the motor on the lift. It had the "issue" again.

At this point, I know it's either the temp sensor or the thermostat. Since I just replace the temp sensor I removed the thermostat, brought it in the house and checked in hot water. It worked as expected. I put back in the motor, restarted and it ran fine.

I ordered a new thermostat and will replace.

I'm trying to understand how the temp sensor/thermostat are tied back to the "issue" of rough idle and stalling when put in neutral.

Any ideas?

[fairdeal]

hmmm. this is a 2006?
so EFI
the thermostat - if it is "stuck open" - might cause the engine to "run cold"
in response the ECM will increase idle but should run strong enough to go in and out of gear
but a "stuck open" thermostat is obvious on inspection...


if the engine temp sensor is giving the ECM "wacky" input - then the engine may run poorly.
But two temp sensors "failing" is implausible -
as is a need to "clean" the temp sensor....

last year - Rodbolt suggested that there might be a problem with the sensor reference voltage -
which would cause GIGO for several sensors -
and certainly cause crappy running

what happened with that line of inquiry?

[ausnoelm]

It's possible the "issue" has nothing to do with either the sensor or the thermostat, but, when it gives trouble, playing around with these parts simply returns the motor back to how it should be, intermittent problems can be like that.

[pstephens46]

It's possible the "issue" has nothing to do with either the sensor or the thermostat, but, when it gives trouble, playing around with these parts simply returns the motor back to how it should be, intermittent problems can be like that.

Returns the motor to how it should be. Very helpful. Is it possible he has a wiring issue to the thermosensor? I would say that is an issue regarding thermosensor.

[ausnoelm]

Simply stating that while fooling around with parts, may allow "something" to cool down, reset, make contact again, just saying that things are possible to happen, not related to the fault, thermostat and sensors are cheap, replace them, then continue on to find the fault.

[pstephens46]

Did this OP ever try using YDIS to point to a sensor issue? Fast idle was mentioned. I did not look back at past thread.

I have a couple friends with Suzuki motors. Sensor issues seem chronic with their motors. Maybe cheaper price is not the best thing...lots of part changing going on with no resolve.

[rodbolt17]

go to da bank.
get 1000 dollars worth of quarters.
toss a hand full every 10 min at the motor. hopefully it cures itself in less than 30 min.
or simply trouble shoot it.
YDIS is great.
each and every sensor/switch can be tested with a SM and a multimeter.

[jackmanjls]

rodbolt17 says...each and every sensor/switch can be tested with a SM and a multimeter.
What does the SM acronym mean?

[walleye1]

Service manual.

[boscoe99]

People talk about testing components quite often. I rarely read about the need to test wiring, connectors, and input to the sensors. Why is that?