Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Revs not going to idle

Does it still do it with the speed sensor disconnected ?

Laurens, have you checked that the throttle cable hasn't frayed or is sticking and holding the throttle open just a little?

Roger, as your suggestion was the easiest, I started with that this morning.
Surprisingly when disconnected, the idle remained normal whatever I did. Drove for +/- 50 km and put the car many times in neutral when rolling. Idle normal.

I came home and connected the speed sensor again.
I went for a second ride, and now idle also normal. Drove +/- 40 km, switching to neutral many times to see if idle would go to 1000r rpm. All the time normal.

Suddenly the high idle started to show up again. Disconnected the speed sensor plug and directly idle was normal.

The problem must be somewhere in the cable or the plug from the speed sensor.
As I tried yesterday by swapping the speed sensor from our other car, which didn't solve the problem, I don't think it will be the speed sensor itself.
Hope it's not somewhere in the cable to the ECU as that's not an easy job.

So thank you Roger, for helping me to search in the correct direction. We owe you a big beer next year in Grindelwald.

Hi Laurens,

Did your speedometer reading appear normal when the speed sensor was connected but revs were high ?

Thanks

Yes speedo is reading all correct.

Thank you. This is probably not much help , but when I had a speedo sensor fault the reading was all over the place which suggests not this sensor at fault - possibly !!!!
I cant confirm was the fault a faulty sensor , or an earth problem etc. but I do know it was replaced and normal operation returned.

Check and clean your earth connections.

Is it possible for you to be more specific about which earth connections and where to look ?

ground connections are a BITCH.... but look for any and every place that the ground wires connects to the chassis

Ground/earth connections are often ignored, but they along with the metalwork of the chassis perform as half of each 12 volt circuit. and can often be the first place in a circuit for poor connections to begin.

Earths/grounds are often ignored, whereas the imagined live/hot side of the circuit tends to be that which is well insulated and waterproofed.

Earth faults can throw up all sorts of issues that seem far less obvious to resolve as they can effect more than one circuit and depending on how many circuits might be grouped at one earth connection point on the chassis, and that the level of crud/corrosion/ looseness of connection can vary with vibration, perhaps related to the number of circuits are switched on at any one time and connected to earth at that one point.

An ideal earth connection would be one where the connection to the chassis it bare metal to bare metal, and that many earth connections can be in out of the way places on the underside, what better place for crud to build up and corrosion to begin..?

It can pay dividends to pay attention to earth connections, and if they are looking corroded taking them apart cleaning them up and putting them back together can brighten lights up, increase charge rates and reduce the chance of failures... Though once you have cleaned all those connections up to the chassis it seems best to give them an overall covering of petroleum jelly, grease or paint to stop the nice clean metal from further corrosion..?