Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) High Idle speed when car is moving

Hi All

My 2013 plus 4 (with the Duratec 2 litre) has strange engine idling. When the car is rolling (but with the clutch depressed) the idle is about 1500 rpm. When the car stops it lingers a second or two then goes down to around 1000 rpm.

Any ideas on this behaviour? Seems odd to me; it means that once the car is moving it wants to go a about 20mph in second!

Might be worth checking out the functioning of the clutch ECU switch, down at the pedal next to the brake switch. Assuming it has one like my 4/4.

It might also be a sticking throttle butterfly. Your description shows striking similarities with issue I had here despite being on an entirely different engine. On occasions it would hold for several seconds 30 mph in 4th or 20 mph in 3rd with foot off throttle, but always reverted to idle when l dipped the clutch.

I had what felt like a “notchy” pedal when taking my foot off. Looking under the bonnet, just where the throttle cable exits the bulkhead, there were several damaged strands, where the bare inner enters the protective outer. Easily replaced and I now give It a touch of lube regularly.

Both excellent answers by RichardV6 and Deejay

Easy way to check throttle cable function is when this is occurring check the throttle cam quadrant at the throttle body and see if you can manually rotate it further to the shut position. if so then inspect cable and throttle butterfly function.

Throttle body is plastic and if for some reason the mech's have taken yours of to clean the MAF sensor and throttle spindle it is very easy to over tighten the retaining jubilee type clip. This pus a force on to the plastic body and distorts it enough to prevent it closing correctly, air can then pass the butterfly valve and the sensors read this as throttle being applied. Solution. Loosen the clip until fully loose and leave it overnight then tighten very carefully and only just tight enough to hold the clip from moving, it really will not feel as though you have tightened it adequately but any more and distortion can occur.

Thanks for your thoughts. However I can eliminate anything to do with the clutch as the behaviour is the same either with the clutch depressed, or when rolling in neutral. The engine runs at 1500 rpm until almost at a standstill, then drops to 1000 rpm. If I’m on a slope I cat let the car roll again and the idle goes up again without touching the throttle. I think that eliminates therottle cable or butterfly sticking too.

It feels like the ECU is controlling the engine to behave in this way.

Have you plugged in an OBD11 and checked for faults ?

I have an OBD reader on order!

Sounds a bit like the ECU's anti-stall kicking in

Some of the Silvertop engines in the 4/4 used to suffer, if you coasted up to a set of traffic lights (no throttle) dipped the clutch, the car would rev up

My car is the same. Bought from Ledgerwood on the test drive it was revving to 3000 when “idling” on the move and was almost undriveable. He said it was to prevent stalling on idle when the engine is cold. They spent some time resetting this and got it to what you describe and I’ve driven it like that ever since. Seems to me there’s a cold idle setting not right but that was the dealer fix