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Discussion Starter #1
Hi all I have been having an issue with the running of my MGF for the last couple of weeks and I haven't managed to get to the bottom of it.
The car starts and idles OK, but as soon as I give it even a little throttle it coughs, splutters then back fires if I hold it down. and makes it un-drivable,
but then in idle it sound very sweet.

I have changes a few things some for new of Ebay some I had spares lying around.
New HT leads.
New dizzy cap and Rotor
new crank sensor, great pain to replace.
replaces the coil with an old one I had lying around.
pulled all the plugs they were all sooty as you'd expect from something miss firing, I cleaned them and put the same ones back.
replaced the throttle sensor with a spare I had lying around.
Checked the Cam belt timing, broke the cam belt cover in the process, every thing seems to line up although I do need a new cam belt as this one appears to be cracking.
pulled the air filter of the throttle body squirted carb cleaner into it, still no good.
Don't think its a blocked breather tube as I pulled one with no difference.

Its leaving me scratching my head wondering what the hell is going on with it.

Anyone experience anything like this before? Could it be a wiring issue?

Cheers.
Dan
 

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Discussion Starter #3
Get yourself a Pscan to get to the bottom of the problem.

One thing that you have not replaced is the cam sensor.....
Early MGF doesn't have cam sensor.
Also not sure pscan supported on MEMs 1.9. sure someone will tell me I wrong?

could fuel pressure cause it?
 

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I have no idea if you have a cam sensor. I have a Jan 1998 VVC and it does! How do I know? I replaced it.

Could be (fuel pressure) - equally it could be lack of air.
 

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Discussion Starter #5
I have no idea if you have a cam sensor. I have a Jan 1998 VVC and it does! How do I know? I replaced it.

Could be (fuel pressure) - equally it could be lack of air.
Sorry I should have said 1997 1.8mpi.
its only done 144 thousand miles.
 

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'06 MG ZR +120 (HQM) '04 MG ZR 105 (IAB)
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........not sure pscan supported on MEMs 1.9. sure someone will tell me I wrong?
....You are wrong :)
The pre- MEMS3 non-EOBD compliant cars were the principal reason why pscan was developed in the first place. As far as the pre MEMS3 MGF is concerned, it will communicate with all ECUs used - MEMS 1.6, MEMS 1.9 and MEMS 2J.
 

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Discussion Starter #7
....You are wrong :)
The pre- MEMS3 non-EOBD compliant cars were the principal reason why pscan was developed in the first place. As far as the pre MEMS3 MGF is concerned, it will communicate with all ECUs used - MEMS 1.6, MEMS 1.9 and MEMS 2J.
Excellent how can I get my hands on one?
 

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Discussion Starter #8
Hi, would a fuel regulator problem cause this?

I had been getting an intermediate starting problem which I thought was down to the fuel relay (will not start until relay pack disconnected then reconnected) but I swapped the relay pack for a used one but the issue continued to occur once a month or so.

So I'm just wondering has some old wiring causing this?

I don't have access to a pscan scanner, if anyone can lend me one.

I've got to a stage where I might just SORN it until the weather is good. save me some money then work on it in the spring.

Cheers.
Dan.
 

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mg_tf
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I've never had this problem but from what I know generally, your engine is either running rich or the timing is delayed. You say your plugs are coated in soot and you get the occasional backfire - well backfiring is fuel/air igniting after it should have done - on the exhaust stroke when the exhaust valve has just opened or maybe a rich mixture causing poor combustion which extends far longer than it should do and overlaps with the exhaust cycle.

I'd be looking at the mixture and/or timing. Timing is fairly easy with a timing strobe. Mixture, hmmm, there was a device called a Gunson's Colourtune years ago - a spark plug with a glass seal. You could see the mixture burning and see the colour, which gave you a fair idea of the mix. The lambda sensor output also measures the mixture.

The fact it idles well must be a clue - timing is not really a big deal at idle so that fits in with the timing theory. Idle air goes through the Idle Air Control Valve (IACV) so poor performance above idle might point at the TPS but you've replaced that.

I wonder if the Lambda sensor could be implicated here? The output of the lambda sensor is used (I believe) to trim fuel delivery to achieve a good mixture and therefore emissions. I believe there is a fast and slow feedback loop whereby the ECU trims fuel delivery (over time) to give a good lambda sensor output, trying to get it to where it's output indicates a good O2 content in the exhaust. if the lambda sensor was bad the ECU might be acting on bad data and trimming the fuel delivery completely wrong. The lambda sensor outputs a voltage so could perhaps be tested by something as simple as a digital voltmeter. You'd have to read up on what the output ought to be. It's somewhere around 1 Volt from memory but you'd need a proper reference for that.

The Pscan would be invaluable no doubt, as opposed to doing it all the trad way, but I think they cost £100.
 
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