[928uk] Temp II Sensor failure symptoms

[Paul]

Out of the blue the engine has just started running rough, hunting at idle,
running rich

I hoping it's just the temp II sensor, or the wiring in the sensor plug

The only thing I've done with the car since it was last running was pull
the fan assembly and fix a wiring issue as one fan was not running

A few days ago I did pull the sensor with a view to fitting a new one, but
the new one was out of spec, so I refitted the original and it's run
perfectly since then until this morning

What else I should look at if I can't find a problem with the sensor?

I have a big trip planned for tomorrow for my gf's birthday, so I'm feeling
very nervous right now!

Paul
87 S4 Manual