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MG MGF Technical - Over-revving

Hi all.
Ive noticed that my '98 vvc has recently started to over-rev at idle. It tends to sit at about 1600rpm, but when I tap the accelerator it drops back down to normal (just under 1000) and then hops back to 1600. However when i pulled up at a junction the other day, clutch fully depressed, the idle was at about 2200, well too high.

Does this sound like an easily curable problem? It hasn't been serviced for a while and is a little overdue one, so could it just be a case that it needs a good tune-up?

Any help...

Mike :-)
MikeR

Initialy it sounds like the throttle position sensor. Easily reset by owners but I can't remeber where the notes are. Basically it involves ignition on (but no engine) and depressing throttle pedal 5 (I believe) times and then ignition off.

Also reset if serviced correctly with testbook.

Anybody else out there with a url ?
JohnP

I have one... but... well hopefully I'll be able to upload tonight, but we seem to be having real problems with firewalls at the moment John :o/
Rob Bell

I had a similar problem which turned out to be the original plastic throttle barrel on my MY2000 vvc. This was replaced by a metal one (Dellorto I believe) under warranty to fix the fault. I think the plastic ones can distort.
Chris
Chris

Yes, throttle bodies can stick due to distortion (if plastic) or through crud accumiliation - which can be clean using a carb cleaner.

If you do decide to replace the throttle body, then an alloy one can be purchased from the mg specialists, in either 48mm or 52mm forms - the former being the standard size.
Rob Bell

Bear in mind, the failure source may be not ultimative át the part that should do actions....
From Mile's description I daubt it's only a sticky throttle butterfly.

Idle @ 1600 revs is almost the fail save mode in the ECU and it's caused by several sensor failure options.

Might be only a bad connection at the water temp sensor, throttle position sensor or inlet air temp sensor and the affiliated wires at the ECU.

I'd recommend looking there before wasting money at dealers and for new parts.

ECU connector (sensor wires colour marked)
http://www.mgfcar.de/mems1.9/mems1.9.htm

Sensor *collection*
http://www.mgfcar.de/sensor/index.htm
(lack of brief English description though)

HTH
Dieter
Dieter K.

Cheers guys, i'll take a look and see if I can figure out what's going wrong

Mike
MikeR

This thread was discussed between 30/09/2004 and 01/10/2004

MG MGF Technical index

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