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MG MGF Technical - Missfire and starting

Hi guys and girls its a long time since i have posted but have a quickie.

I have had problems recently which i put down to the damp weather even though the car is park in a garage overnight..

I have problems with the car misfiring and stuttering then if i switch the engine off it wont start for about an hour or so, this makes no difference when the engine is hot or cold will do it anytime but seems to be when it has been raining, i have had a service recently so all the dizzy ca, plugs, leads etc have been changed, also i dont know whether it is related but the front fan seems to be on quite a bit which i find strange in this weather......

Hope that makes sense
BTW its a 96 MPi......

thanks for any help
Nick
Nick Walters

>>i have had a service recently so all the dizzy ca, plugs, leads etc have been changed, also i dont know whether it is related but the front fan seems to be on quite a bit which i find strange in this weather......<<

Hi Nick,

are you sure that all these ignition components have been replaced? I ask, because parts like the dizzy cap and rotor arm don't seem to get changed during routine servicing...

Definitely worth checking again.

The rad fan being on is a little odd. Water temperatures are normal? Or is the car running cooler than 'normal'?
Rob Bell

Hi Rob

No all the temperatures seem exactly the same

i know the other parts were changed because i changed most of them before it went in for the service as i had another problem i wanted to cure. so i changed all the ignition parts...
Nick Walters

Could be the temp sensor for the ECU, it's diffrent to the one for the gauge so the temp will appear fine, but the ECU thinks the cars cold and over fuels causeing the hesitation.
Will Munns

That was what I was thinking Will - but one might expect the water temperature to be lower if this were the case?

Nick, it is sometimes possible that new components can be faulty - it's happened to me before with ignition parts on my dear old Triumph... Something to bare in mind if the problem can't be traced elsewhere.

Apologies for the next question - what was the spark plug gap set to? I'm sure you did this correctly, but trying to see if there are any other causes of an ignition problem.
Rob Bell

Is the water temp guage in any way sensitive enough to show small differences in water temp? Apart from the intial warm up I've never seen itat anything other than one notch below half way.

For the cost of a new coolant temp sensor, and the ease of replacing it, I'd try that and see what happens.

Dave
Dave

Nick

Not sure about the misfiring but I had a very simalar problem on an Escort I owned with regard to it not re starting. It would start fine in the morning, I would turn off the engine to fill up and then it would not restart, would not even turn over. This happened in all weather conditions and was intermitant, would always start eventually though.

Every time I tried to show a mechanic it would always start, on one occasion I called the AA and with one swift hit to the starter motor off I went, replaced it the next day and it never happened again, turned out it was sticking when the engine heated it up.

Hope this is useful

Arron

Arron

>>Is the water temp guage in any way sensitive enough to show small differences in water temp?<<

Valid point Dave. No, it isn't especially sensitive - see Dieter's page http://www.mgfcar.de/sensor/index.htm

But in order to get these running problems, I would expect to see some evident change to the steady-state operating temperature?
Rob Bell

Thanks guys,
I will try the temp sensor for the ECU first
is this an easy job for an amateur or a dealer job....
any tips if anyone has done it

thanks
Nick Walters

This is a *Rob Job DIY*.
See http://www.mgf.ultimatemg.com/hgf_diagnosis.htm
Includes the change
Dieter K.

Nick - if I can do it it's dead easy. Check the workshop manual if you have one, but from memory

* Engine cover off
* Locate sensor - IIRC it's brown and roughly in the middle of the engine towards the cabin bulkhead
* squeeze circlip and pull off connector.
* Unscrew sensor enough to be able to remove it by hand, but don't remove it yet
* get the replacement in the other hand - ready to do a quick swap
* unscrew the old sensor completely and whip it out of the way, slapping the new one in place quickly, so that you only lose a drop of coolant
* screw new sensor in
* re-attach lead
* before replacing engine cover, fire up engine and leave it idling to check that the radiator fan cuts in after about 15 mins

If I've missed something obvious or got something wrong, someone will be along soon to correct me.

HTH

Dave
Dave

>but one might expect the water temperature to be lower if this were the case?
Nope, the fan just simulates airflow like running along a road, the thermostat (mechanical) takes care of mixing the radiator/bypass coolant to keep the temp constant.

Will
Will Munns

This thread was discussed between 10/03/2003 and 11/03/2003

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