Yamaha F250 3.3l bad idle

[ghpeddie]

Hi
hope someone can help
3.3l V6 F250 starts fine idles fine for a few seconds then surges , drops rpm then most times dies.
rest of rev range is fine , we have swapped over all sensors, looms throttle body everything.
ydis shows no errors.
any advice
2017 model with 3000hrs
posting from South Africa

[99yam40]

is the idle air control valve working properly?
do you hear it rattle( resetting for next start up) when you shut off the motor?

[ghpeddie]

What I have been told is these motors don’t have the IAC as it’s con*****ed by the single throttle body.
both motors don’t rattle once switched off.

[99yam40]

so how does the ecu control the idle if it does not have an IAC?
I guess you could look in the parts break down

[boscoe99]

Electronic throttle valve on that model. No IAC valve. The ECU varies the opening of the throttle to manage the idle RPM.

The control cable tell a gizmo what the throttle opening should be. That gizmo then tells the ECU how much to actually open the throttle valve.

[boscoe99]

What is the compression?

What is the fuel pressure?

YDIS will not tell all.

[ghpeddie]

Compression was checked a while back and all good , fuel pressure is fine and last night we swapped over VST tanks just to make sure, still the same.

[99yam40]

just because compression and fuel pressure was good / fine before the problem showed up, does not mean it is fine now.
numbers would help others know what you consider good and fine

well if no IAC then something is out of wack, so finding that needs testing while the problem is there

[ghpeddie]

Thanks
the problem has been around for a while , compression tested , fuel pressure tested. Basically the whole port engines electronics are on the stbd engine but still it does it!

[ghpeddie]

Hi all
just thought I would give some feedback on this idle issue.
turns out the insulation on the wires going to the stator perished and the wires started corroding , swapped out with new and the problem is gone!