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MG MGF Technical - Engine revving in neutral (MGF)

I'm hoping that this is a stupid question and is normal, but being a bit of a girl about cars this owning an MGF thing is all new to me!

I bought a 95 F last week and have driven around 200 miles in her so far - with no problems. This morning I drove to work in her for the first time, and noticed that when I stopped in traffic or at lights and put her into neutral that the engine continued revving - up to around 3000rpm.
I've not noticed this happening before, but this is the first time I've driven a shorter journey with lots of stops and starts - is that anything to do with it?

Is this normal? Am I doing something wrong to cause this?

Thanks for any advice you can give me!
Danika

Sounds like a brown sensor failure, or a TPS sensor failure.

If its is TPS then switching the ignition on, 5 presses of the gas and then off before switching back on and finally starting the engine should cure it for a while.

If it's brown temp sensor then the plug might have dirt in it, there might be a fault with the wire, or the sensor might need replaceing. Other effects _may_ (or may not) include the fan running non-stop (you may have to be in front of the car to hear it)
Will Munns

Hi Danika,

This worked for the last person to report this problem:

Remove the grille panel under the bootlid, peer in and you'll see a plug connector poking up at 45 degrees, that's the TPS (Throttle Position Sensor) connector. Unplug it and give it a generous spray with electrical contact spray (Maplins/DIY store/car accessory shop)and re-connect.

Give that a try, let us know how you get on.
Mike Hankin

I agree with everything that has been suggested so far - but want to add one more thing on the list of things to check: the throttle cable.

If the accelerator is a bit stiff or feels a bit jerky, then the cable may be sticking. You'll be able to confirm this if, when the car is idling at 3000 rpm, check that the throttle is completely closed by rotating the throttle cam clockwise. It shouldn't move, but if it does, then you have your answer.

One other candidate that Mike has inferred, but not directly mentioned, is the Idle Air Control Valve - which can gum up with oily residue over time. It responds well to a quick blast with carburrettor cleaning spray (some have even used WD40!) - but I'd check all of the above first, as the IACV takes a little more work to remove in order to clean.

HTH
Rob Bell

Dont forget the crappy black plastic throttle body ! This one tends to get more squeeky and stiff year by year. And mine even got worse when hot...
Finally gave up and fitted the big bore alu one.
Carl

Hi Danika,
I to have recently bought my first MGF VVC and had the same problem with high revving.
Took it to a garage and they basically did the same as the comments you have received so far i.e. check/clean sensors and connections. They also said the throttle inlet was all carbonised so cleaned accordingly (£3.25 for Carb cleaner).
Job now done and engine purring!!
Good luck
Paul..
Blackers62

hi rob or mike
am going to clean my sensors tonight as you said on the last message ....
under the grill which ones could i tackle with the maplins spray then????
darren mk
darren jeffery

bad news, the sensor in right in the middle of the bay but on the front of the engine, so you have to remove the parcel shelf to get at it. for this you will need a 10mm spanner
Will Munns

Yup - you'd need to be one of the Incredibles - the one with the elasticated stretchy arms to reach the engine coolant outlet stub - and X-ray vision would help too! LOL ;o)

Unfortunately, as Will says, the inspection cover needs to come off Darren - but this won't take you too long to do :o)
Rob Bell

Dani not darren
Will Munns

and if you don't have the spannerage then I would suggest a ratchet spanner.

Don't do them up tight when you replace, just 'snug'

the clip comes off by squezzing on both long edges to compress a wire spring and then pulling in the obvious direction.
Will Munns

Darren, the connector I was giving directions to is the TPS, which is one of the possible culprits, but the high revving can also be caused by a dicky connection on the ECU temperature sender, which as Will & Rob have lamented is only accessible via the inspection panel. There are two sensors right next to each other, one is brown (ECU temperature sender) and the other will be either black or blue, that one feeds the dashboard gauge.
Mike Hankin

Many thanks for all your help - boyf and I had a poke around in the boot earlier and it now seems to be fine, so will keep an eye on it, and if the problem comes back I'll try out all your suggestions!

As a new owner (just over a week now) it's really nice to have the support of this forum while I learn about my car - makes owning it fun rather than scary :-)
Danika

< boyf and I had a poke around in the boot earlier and it now seems to be fine> Must try that next time the car gives trouble...who said'you can do it in a MG'???;-)))
Paul

Hmmn - no comment...

Danika

This thread was discussed between 05/06/2006 and 06/06/2006

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