Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Unidentified sounds in silence

On a number, of occasions when I have been in the garage, I have been surprised to hear my Brooklands M3W 'chatting to itself' for no apparent reason. Cold engine and ignition off. In my ignorance a cursory investigation failed to find the source of the very intermittent sounds and I assumed that "they all do that Sir". I was however concerned about a potential drain on the battery. More recently an 'Elder Statesman' of the marque had my trike in his garage for some TLC and was intrigued when he heard the same sound. He traced it to the stepper motor activating the idler air valve, but in spite of his superior knowledge and diagnostic kit he was unable to establish why it continues its occasional and intermittent running.
Has anyone any ideas?

Take more water with it or contact the local vicar to exorcise it ? 🤔

I'm not aware of mine doing it. I think I would have noticed.
Have you seen any other signs of electrical gremlins? I assume the ECU is making it do this, but perhaps it is confused about if the car is running or not?

This is priceless!

However such a sound would make me think a problem with the ECU since it is still on to some degree when the ignition is off.

Thanks for your various responses:
Taffmag: I spoke to the Vicar but he only wanted to talk about the Trinity. I guess he was talking wheels.
JohnMat & Lightspeed,. No other signs (or sounds) of electrical gremlins. Yes, I guess the ECU is at the root of the problem. I was hoping that someone would suggest a cure.
I'll await further advice. I'm a patient man.

I have a similar gremlin with my trike as it adds mileage to the odometer while sitting peacefully in the garage. It became a real challenge with the disfunctional fuel gauge by eliminating the 200 mile fill-up process so I invested in a GPS speedometer / odometer to keep track of things. Thankfully it reconciles to the mileage reported by ProTune when connecting to the ECU. Another bit of "quirkiness" that makes them so endearing.

Fit a battery disconnect. Solves many issues.

Do they not have a cutout switch already?

They maybe don't "All do that sir" but my M3W does it sometimes as well. If the ignition has been switched on and then off you can hear the Idle Air Control Valve motor intermittently for an hour or more after, not every time but sometimes. My car has had different ECU's fitted and that has made no difference, so probably not the ECU. It's been doing it for years with no problems, forget it.

Just take the earth lead off the battery and see if it still does it?
It may just be expansion/contraction inside the silencer. Even a degree or two change in air temp can cause this as silencer internals are usually an interference fit rather than being welded to the case.