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MG MGF Technical - Replacing ECU

I am considering replacing my ECU with one from Ebay to get round a management problem. How do I get round the immobiliser which will expect tosee the original keyfob?
Brian Highe

You will need to get the replacement ECU coded to work with the existing immobiliser unit (I presume the Lucas 5AS - but you don't mention the age of your car or the version of MEMS you seek to replace?)

In fact taking some time on Testbook is probably sensible any way, as the ECU may require some recalibration to use with your engines existing sensors - such as throttle position, MAP etc.

What is the problem you've got with your ECU?
Rob Bell

It's a long story which starts with a tickover that sometimes settles at 900rpm and sometimes at 1500rpm. Since then I have checked and finally changed the throttle body, coolant temperature sensor and IACV. I have also cleaned all the connectors and checked the wiring between the sensors and the ECU. So I have run out of ideas other than trying a replacement ECU.
Brian Highe

You need to make sure that the ECU on eBay has exactly the same number on it or it will not work on your car. Different ECU numbers were used depending on the options fitted (ABS, ePAS, etc.). You should also only buy it if it comes with the 5AS unit (you will need to get your fobs synchronised to the new 5AS unit if the fobs are not supplied), otherwise you will have problems the next time the car is connected to T4.

This assumes that your car has the square type fob. If your car has the round type key fob its a completely different ball game.

Ralph
Ralph Gadsby

>Since then I have checked and finally changed the throttle body, coolant temperature sensor and IACV. I have also cleaned all the connectors and checked the wiring

Did you consider plugs and leads or distributor failures also ?
Might be worth to just changing the rotor arm and distributor cap if it's a standard old MPi MGF (none VVC)
Dieter

At last, after reading this BBS for many years I can talk to the great Dieter Hersfeld but ...

It's a VVC and the leads are newish silicone.

The tickover never falls below 950 but at least 50% of the time setlles at 1500. I cannot see how plugs or leads would cause this.
Brian Highe

There is guy on the roverorg forum (Kris) who has sorted a few people out with MEMS repairs and testing see his mems unlocking advert:

http://stores.ebay.co.uk/TheSlashShop
Jon Baker

Does it have a plastic throttle body? If so that may be the problem, apparantly they can distort which cause them to stay open. Although you have replaced it already if you replaced it with another plastic one that may be faulty itself. I had this problem with my 2000MGF and fitting an aluminium thottle body fixed it.

Regards

Andrew Smith
Andrew Smith

I had a similar problem when my K&N fell off, though I doubt that is relevant in your case. I dont know if it was the extra air flow or grot keeping the butterfly valve from closing which caused the symptom, but blipping the throttle often allowed it to return to normal idle speed.

Pete
P Davey

After trying everything and as a last resort I bought another plastic throttle body on Ebay for £8. After fitting it the problem is still there but with a slightly higher tickoever so I think I have ruled out the throttle. Also, by blocking up various orifices, I have proved that the additional air is getting in through the IACV and not via the throttle. Incidentally, I have changed the IACV as well and checked the wiring between it and the ECU.
Brian Highe

Brian, have you checked the throttle cable?
Maybe it is to tight.

Arend Groen

Brian

I take it you have reset the TPS after installing the new body..

Silly question probably but worth asking

Stu
Stu Dickens

hiya doing.not a happy camper.ave 98 mgf.it seemed to b spluttering when its idioling.loosing power too.brought it to main dealer,plugged it into the computer.its given no reading.basically they told me they can do nothin for me.hope u can help me here.thanks
ian

Ian, most likely cause of this problem is the O2/lambda sensor. This should be picked up by the T4 diagnostic computer. I assume that the dealer was unable to connect to your ECU for some reason or other.

Ralph
Ralph

hiya.my 98 mgf is given trouble.its spluttering.losing power,cutting out on me.brought it to main dealer.they can get no readin at all from their computer,hence cudnt find fault.ther computer cudnt give them any reading.anyone know of of this problem.why cant its diagnosis give a reading.im not ver happy and i was an mg fanatic.please help
1an

@Ralph:

Don't think "Different ECU numbers" will be a major problem, in fact, I've currently got a Rover200Vi MEMS2 running on my former MGF MPi which is nou equipped with a working TF160VVC (K06A) head :)
Sander

>> hiya.my 98 mgf is given trouble.its spluttering.losing power,cutting out on me. <<

You didn't mention which engine your MGF has? If a 1.8i, I would suspect the rotor arm and distributor cap first, as these items don't seem to get replaced regularly and cause the problems you're experiencing.

More here: http://mgf.ultimatemg.com/group2/common_problems/distributor/stuttering.htm
Rob Bell

This thread was discussed between 26/06/2007 and 12/07/2007

MG MGF Technical index

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