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MG MGF Technical - VVC idling to fast

My 1996 VVC idles at 1800rpm, so I reset the stepper motor (run to normal temp, switch off, switch to ignition position two, depress the throttle fully 5 times, wait 15 seconds, switch off and re-start. The engine then idles at 850rpm for a while, maybe up to 2 days, sometimes just an hour then goes back to idling at 1800rpm.

Anyone got any ideas whats going on? And more importantly, how to fix it, before I end up sending several hundred pounds at my local MG dealer.
Nicolas Hawke

Nicolas,

You possibly have a sticking butterfly valve in your throttle body or a noisy throttle position potentiometer. By noisy I mean that the signal from the pot is not smoothly rising and falling with the position. The greatest wear takes place where the throttle stops at rest, so the pot may be wearing at that point.

I can lend you a throttle body and potentiometer to try out if need be. I am near Rugby, so not far away.

HTH

Bruce
Bruce Caldwell

Bruce

Thanks for replying.

I appreciate your advice, and will look into the possible answer. Can you send me your email address in case I need to take you up on your kind offer.

Regards

Nick
Nicolas Hawke

Nicolas,
I had the same problem on my VVC for a ong time - I fitted a new Trophy TB and the problem is now gone - it must have been a sticking throttle buterfly valve.
If yours is a similar problem then it would only cost around 120 annd 30 mins to fix and as an added benefit better performance if you fit a Trophy TB.
Jason H
Jason H

Nicolas,

if you got a jubilee clamp at the connection between throttle body and intake hase, than this could be the initial reason for a bent TB. If this clamp got tightened to much then the part got bended. (K&N user may notice). No help but changing to a new one IMO.

First aid on checking the TB flap condition is to access it by hand. If it squeaks or feels difficult to open, than just forget it and get the Trophy part to replace. Dismanteling the old complete down in pieces and grease the axle at the grey coloured washers inside is another option but so boring. :)

HTH
Dieter
Dieter Koennecke

This thread was discussed on 19/03/2002

MG MGF Technical index

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