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MG MGF Technical - High Idleing Speed


Just picked up a 1997 MGF - less than 40K on the clock. All well - except excessive idling speed of around 1500 revs. Is this easily adjusted? Is their any likely fault that could cause this - e.g. Auto choke issues??


Could be the stepper motor needs resetting.

To reset it switch off the engine, turn on the ignition but DO NOT start the car, dash lights should be on, then depress the throttle pedal 5 or six times fairly sharply, then start the engine - this should reset it for you.
Chris Catchpole

Thanks Chris. Will give it a try.

J Martin 1

If Chris' solution doesn't work then look at - which lists the commonest causes of a high idle speed...

Good luck! :o)
Rob Bell

Thanks Rob. Chris's solution improved it a little - it does drop to around 1000 rpm occasionally. Incidentally - The manual is in the car (Wife has it!) I recall the idle speed to be a maximum of 1250 +/- 50. Is this about right? If so - Is the idle setting now okay. i.e. Is this a high revving engine - even at idle?


J Martin 1

Should be about 850 revs only.

If the reset improved then the problem relates probabbly to bad electric contacts at the throttle position sensor (TPS) or at its connection to the Engine Management System. (MEMS ECU) Any problem with underpressure system or inlet air temperature sensor could be as well.

Could be any sensor which failure forces the MEMS ECU to _fail safe mode_. (Idle higher than usual)

How does it work in driving speed when you kick the clutch and release the accelerator pedal ?
Does the engine rev down to idle smooth and quick ? Or is it used to rest at higher rev's and go down very slow ?


Dieter K. @ work?

Hi Dieter

It reduces revs slowly.

Engine quickly rises to operating temp of half way on the gauge.


J Martin 1

I too only recently obtained this problem and I am reasonably sure that in my case it is a bad connection on the MEMS. I can say this as I had to remove the mems when taking the passenger rear shock off. So it would seem logical, I hope, that it is the mems connections. Armed with some contact cleaner I will venture out once it gets above -5 degrees.
S Laithwaite


just forget that gauge reading.
However, slow increasing to idle indicates (IMO) direction bad connections and _fail safe mode_.

Have a go for checking the connections. Stephen and some more experianced the same.
I my case the only _disconnect/re-connect_ of the large black coloured ECU connector and re-alignement of the connected wires cured the problem.


different problem, but matters the same I said above with connections.

Dieter K. @ work?

> I had to remove the mems when taking the passenger rear shock off

On an F or TF?
Bob Millar

Throttle position sensor - or wiring to it.
Rare fault, but produces the slow drop in revs you refer to.

Paul Nothard

Bob, on an F. It was just easier trust me.
S Laithwaite

Thanks all

I will have a look on the weekend.
J Martin 1

> Bob, on an F. It was just easier trust me.

Dont know how, I managed to remove my shock without removing the mems.

You just need a really long socket extension
Bob Millar

Well - thanks all. Doesn't appear to be a wiring issue - off to the MG Garage I guess - (Getting worse and occasional drop of power)

If it is anything interesting, I will let you all know!

J Martin 1

This thread was discussed between 04/03/2004 and 13/03/2004

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