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Wales
by Joske Vermeule, September 1
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Forums39
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Jun 14th, 2026
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Joined: May 2012
Posts: 4
New to Talk Morgan
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OP
New to Talk Morgan
Joined: May 2012
Posts: 4 |
Does anyone have any ideas why my Plus 8 is revving up to 2000rpm when in neutral, it also pulls away when I am not pressing the accelerator? I have had it serviced, initially had the stepper motor cleaned, when that didn't work, had a new stepper motor fitted, but I still have the same problem. Anyone have any ideas?
Thanks
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Joined: Aug 2008
Posts: 2,515 Likes: 1
Talk Morgan Expert
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Talk Morgan Expert
Joined: Aug 2008
Posts: 2,515 Likes: 1 |
It always helps if you give the year of the car.
1972 4/4 2 Seater
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Joined: Jul 2007
Posts: 27,846 Likes: 765
Member of the Inner Circle
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Member of the Inner Circle
Joined: Jul 2007
Posts: 27,846 Likes: 765 |
My +4 did that. A 97 T16 engine model it was the ECU. When replaced the problem went away
JohnV6
2022 CX Plus Four
2025 Renault Scenic Alpine etech "Yvette"
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Joined: Nov 2010
Posts: 167
L - Learner Plates On
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L - Learner Plates On
Joined: Nov 2010
Posts: 167 |
Possibly an air leak in the induction downstream of the throttle?
'65 +4 four seater
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Joined: Dec 2008
Posts: 22,371 Likes: 354
Roadster Guru Member of the Inner Circle
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Roadster Guru Member of the Inner Circle
Joined: Dec 2008
Posts: 22,371 Likes: 354 |
I seem to recall that low battery voltage can upset the ECU on Plus 8's?
Also the MAF sensor may need a clean, if not already done.
DaveW
'05 Red Roadster S1
'16 Yellow (Not the only) Narrow AR GDI Plus 4
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Joined: Jul 2007
Posts: 27,846 Likes: 765
Member of the Inner Circle
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Member of the Inner Circle
Joined: Jul 2007
Posts: 27,846 Likes: 765 |
Air leaks can do it so can the valve that lets petrol vapour from the activated charcoal canister if it sticks.
There is a lot on Gomog on +8 ECUs etc. As we don't know your car's age that could be a good starting point.
JohnV6
2022 CX Plus Four
2025 Renault Scenic Alpine etech "Yvette"
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Joined: May 2012
Posts: 4
New to Talk Morgan
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OP
New to Talk Morgan
Joined: May 2012
Posts: 4 |
Sorry, it's a 2002 Plus 8. It's been back to the garage 3 or 4 times now, but with no joy. Initially they cleaned the stepper motor, but that didn't work, so they put a new one in and that hasn't worked either. The Morgan factory then gave them a sequence to drive at certain speeds, but that hasn't worked either. It doesn't happen straight away, but then starts to feel its pulling away when not pressing the accelerator. When I start the engine it revs above 2000.
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Joined: Jul 2007
Posts: 27,846 Likes: 765
Member of the Inner Circle
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Member of the Inner Circle
Joined: Jul 2007
Posts: 27,846 Likes: 765 |
The stepper motor was what they did when my ECU failed. Try this lot http://www.gomog.com/allmorgan/plus8.html
JohnV6
2022 CX Plus Four
2025 Renault Scenic Alpine etech "Yvette"
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Joined: May 2012
Posts: 4
New to Talk Morgan
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OP
New to Talk Morgan
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Joined: Sep 2007
Posts: 478
Learner Plates Off!
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Learner Plates Off!
Joined: Sep 2007
Posts: 478 |
The stepper motor would get my vote. But as DaveW says low voltage can cause the idle to increase, but won't cause it to hunt as seems to be your case? Has the ECU been plugged into a diagnostic unit? Look here for David Poole's remarkable book on Gems
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