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MG MGF Technical - High engine revving whilst stationary

Hi Folks,

My wife just recently bought a 99T MGF VVC from my sister. It had
only done 17k miles and was in great condition. However, just recently
we have noticed that sometimes the engine revs to 3k/4k and
sometimes 5k when stationary. It has also occurred a couple of times
when applying the brakes to stop and then depressing the clutch with
no foot on the accelerator. It can continue revving for quite a few seconds
(with funny looks from bystanders) with the only cure to switch off the
engine! It had its major service only 4/5 months ago.

I would appreciate any ideas.

many thanks
Donald
Donald Cameron

Donald

I had a similar problem.

I've replaced throttle body, which has given me an irrregular idle instead now. oh well.

Think the first thing to check would be if throttle body is sticking?

Also check that the carpet isn't getting stuck between chassis and accelerator pedal.

Easy, cheap things to check.

Although there's a whole host of more expensive reasons it could be happening.

I'd be interested to hear how you get on.
(Mine is a 97 Mk1)

Paul
paul weatherill

Donanld

A Sticky Butterfly valve in the Throttle body perhaps. If you have a black plastic this can get deformed and stick. A great excuse to go for an Aluminium Trophy Throttle body £100 and easy to fit (with a flat 8mm ratchet spanner) :o)

Others will be able to confirm if there are other causes.

Tim
tim woolcott

Bloody hell Paul, that was quick.
tim woolcott

or air leaking into the inlet system - are your brakes OK?
Get hold of some "cold start" and spray a bit around the inlet manifold/throttle body etc.
BE CAREFUL THIS STUFF IS HIGHLY FLAMABLE
if the engine changes note at all then you have an air leak

Or you might have a faulty Idle bypass valve, this will give a simmiler 'feel' to an air leak, because it is one, just thru official chanels! I think you can clamp the pipe, with the engine hot this should sort the problems, if so then replace (or at least look around here first).

Or you might have got some dumb data in the MEMS, switch on ignition( not engine, just all the red lights), fully depress and release the accelerator 5 times, this should reset the throttle position sensor.

Most lightly the throttle itself, then the MEMS, then the other two.

Will
Will Munns

Donald

The same thing happened on my 97 VVC. I removed the TB, stripped it down and cleaned it up, although nothing really looked worn. It's been okay for the last six months. Total time 1.5 hours - its quite an easy job, hardest part is removing the four TB bolts. Small spanner required (length wise!)

HTH.

Nick
Nick

Sounds like the idle air controller to me, similar to a problem I had. Fix is in the archive, or you can just replace the part. An easy way to diagnose this problem is by clamping the air bypass tube on the top of the inlet manifold. Be aware you will have some difficulty with cold starting with this temporary fix.
Grant Vowles

Interesting Grant.

Can anyone expand on this?

paul weatherill

This thread was discussed between 24/10/2002 and 25/10/2002

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