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MG MGF Technical - Idle revs? Help


I noticed yesterday that my my f is not moving, but the engine is running the revs stay at 1500 revs. Im sure this used to be lower than this? Could it be a problme with the choke??

Steve Marsh

discussed many times:

go to dealer and ask to retune your stepper motor, takes about 5 minutes of work once it is connected to the testbook PC (with a nice rpm graph they retune the idle revs to 800/900)

if this doesn't help, ask to have checked the accelerator if it gets resistance somewhere, so it gets stuck. Also check the butterfly thingy throttle body if that needs some grease to loosen it up again

if this doesn't help (revs keep varying) check the solenoids if they're dirty or broken. 1 for MPi, 1 for VVC

if this doesn't help ... erm, some temp sensor broken, but I'll leave it to the others ;)

Close Dirk. :-)

You can reset the stepper motor yourself:
Ignition on, depress the accelerator 8 times, ignition off, start car.

Could be gunged throttle butterfly:
Take tube off throttle body and carefully clean inside with rag. Don't let anything fall in - obviously. :-)

Could be malformed throttle body:
Got a KnN filter ? Tightened it up too much maybe ?

Would feel resistance when moving throttle by hand far the last two.

Finally could be TPS (Throttle position sensor).
Best get the dealer to check this out with testbook.
Can be fixed at home. If you really want, mail me for details.

As Dirk suggests, a common-ish problem. Have a look at the archives for more info.

Paul Nothard

I have this too, my car is just over a month old with 3,000 miles. It used to sit on 800rpm and now it's more 1,100 - 1,200 rpm, I do have a K & N. Is it normal?

Not normal. Needs to be fixed.
See archives or dealer for details... :-)

Paul Nothard

Steve, any problems with coolant temperature?

I ask because I had a similar problem, with the car always behaving as though it were cold- high rpm being held as though the choke was kept open. The clue was over heating in traffic as the radiator fan failed to trigger on.

The problem as it transpired was down to a failed ECU temperature sensor- the ECU thought that the engine was cold all the time, and hence the high idle speed. Simple fix- directions on the replacement of this 10 quid sensor are on the HGF link from

Ashley, I suspect that you have a different problem. If you car has a plastic throttle body, then the jubilee clip on your K&N sounds as though it could have been overtightened, distorting it and causing the throttle to stick. Take it back to the dealer who fitted it for you to investigate further.

Rob Bell

Hi Guys, Thanks for the info.

Rob, all teperatures seem ok, the oil, goes up to about 120 max (after a long had thrashing) and the water temp on the dash never seems to move anywhere past half way. The Fans do sometimes come on when I stop however...

Saying all this yesterday and today the revs were back down to 800, maybe somthing got stuck somewhere??

Ashley..i recon your is a knackered! Sell it and buy another Astra!!
Steve Marsh

Steve, your problem sounds more like a dirty throttle. Black gunk tends to gum up the normal operation of the throttle. You could try removing the filter and spraying in some carb cleaner or similar to clear the crud away and free up the operation of the throttle.

Rob Bell

I have my first service this Saturday, I'll get them to look at it, it goes above 800rpm when I have not been using the car ie first thing in the morning, then after a short drive its back 2 normal, is this the automatic choke?

Bloody cars!


Until the car is at normal running temperature it is normal for the revs to be a bit on the high side - on my *F* they are at about 1000 until warm anon my BMW they hover around 1500 until warm bothe then drop to the 750-800 mark.

BTW in other thread you say you have rattles! I had a ride quite recently in a Rolls Royce soft top and that in line with all soft top cars had the odd rattle as well.

Ted Newman


Sorry to hear about the possible problems. Yes, the revs are deliberately held higher at first but they should then fall as the car warms up. Otherwise, the tightening of the K&N could well be the culprit, but I doubt that the presence of a correctly-tightened K&N could increase the idle revs.

Which bit of the car's rattling? I had a couple of niggles with the car at first (passenger seat slidey mechanisms stuck and one side repeater indicator not working), but these were sorted out fine by Marshalls Rover (Cambridge).

Don't fret too much - the warranty period's your chance to sort all these things out!
David Bainbridge

This thread was discussed between 16/07/2001 and 17/07/2001

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.