F90TLR rough idle

[jackmanjls]

I got up this morn and check the continuity from the ISC connector to the ECU connector. There was continuity for all 4 wires. So that's not the issue.

With the cover off I listened for the rattle sound of the ISC and couldn't hear. I had my ear and finger on the ISC and didn't feel or hear any rattling noise. I'm assuming that it's an obvious sound. I started/stopped several times and never heard the noise.

NOTE: one time when started the idling seemed to run normal but all other times it had the loafing idle.

Is there anything I can do to verify the ISC is the problem. From what RB17 says it sounds like it's stuck in the open position.

The part on boats.net is $210+shipping.

At this point the issue seems to point to the ISC. Is there anything that could be suggested that I could do to absolutely verify that this is the issue? Perhaps jumper the pins at the ISC connector to trick the ECU into normal idle operation. Can this be disassembled/cleaned, probably not?

I'm wide open for suggestions.

[99yam40]

With a laptop , connector, and the Yamaha software you can test it.
Have read if it is stuck it can overheat the ECU and take that out also.
Not sure if that is on all motors or not

[jackmanjls]

99yam40...I googled "yamaha test software" and didn't see anything that I thought was it. Can you be more specific on exactly what I would google to get availability? Or reference where I would buy?

[almetelo]

YAMAHA YDS diagnostic system/software

[rodbolt17]

whoa whoa whoa
I never said ANYTHING about how it was stuck.
I did say at engine shut down you should hear it rattler as it resets to 100% for the next restart.
the ECU DOES NOT monitor the ISC.
its why there are NO ISC codes.
the ECU sends an ISC REQUEST then ASSuME's the ISC moved.
if the ISC is stuck and cannot physically move the RPM wont change but the ECU will continue toggling the ground path for the ISC stepper motor.

that's when the ISC overheats,the ECU overcurrents/overheats and the ECU fails.

the ECU supplies the ground path for the ISC motor, it has 12V+ anytime the key is on.