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MG MGF Technical - Engine misses/hesitates after 5 minutes

Just recently after the batery went flat, every time after about 5 minutes from cold my MGF misses/hesitates for about another 5 minutes. Then it runs perfectly. I have twice tried injector cleaner in the tank but makes no difference. Any clues please?
regards Terry
Terry BANKS

I'd suspect ignition system / MEMS, have you serviced plugs, caps and leads recently? If all this is ok it sounds like the engine is a bit confused during warm up, this could be related to temperature senders and how these are interfacing with the MEMS (as this is all computer controlled). I recall there is a way of resetting the MEMS but have not direct experience of it myself.

Good luck, Russ
Russ68

Thanks for your reply Russ. I will clean and check these parts this weekend as you suggested. I wonder if anyone knows how to reset the MEMS or who can do it here in Tasmania if needs be.
Terry BANKS

I think the MEMS reset thing may have only related to TPS as mentioned in the below link:

http://www.mgf.ultimatemg.com/group2/DIY/simple_procedures/diagnostic_tests.htm

A brief Googling of the issue turned up this, not sure of relevancy, but it may help:

http://www.british-cars.net/mgf-technical-bbs/rough-idlestuttering-and-lack-of-power-200708120324205872.htm

Good luck!
Russ68

Terry,

I had this problem which went away when the car was warm/hot

turned out to be a problem with the coil, for some reason when cold the coidl would go faulty but when warm it was fine.

Not saying its your solution but thought I'd mention it as you said it was only when car was cold. Obviously other possibility is the fueling/ air when cold as mentioned

Brian
B Buick

As suggested I checked the distributor and found that the centre sprung loaded carbon brush was completely burnt away. I have ordered a new cap from England and await its arrival. Whilst I was at it I also ordered a new rotor arm, leads, plugs and engine management relay. But I reckon the knackered cap is the problem. I am amazed it was working at all. I will set the new plug gaps to 0.9mm. Thanks to you all and I will keep you posted of my progress in about another weeks time.
Terry BANKS

Hi Terry, hope the parts we sent arrive safely and cure your problem. Dave Kar-Solutions
David Karle

The new distributor cap, rotor, leads and plugs arrived safely from Kar-Solutions England. It was of course the burnt out brush in the dizzy cap. My MGF is now a 'pocket rocket' again ready to enjoy our Spring weather in glorious Tasmania, home of Targa! Thanks to everyone for your helpfull suggestions. And thankyou Dave Karl for your staff's wonderful service.
Terry
Terry BANKS

This thread was discussed between 18/08/2010 and 08/09/2010

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