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MG MGF Technical - acceleration loss

(I posted this in another thread but think worthy of its own because of a sinking feeling i have!!).

Picked up a steptronic 2000 (w) yesterday and it has lost all accelaration power on 2 occasions now, engine turns over you drive off then just starts to idle(pedal to floor, nothing, like car is in Neutral, but engine is still trying...). Had to pull over, turn engine over and it comes back..... Both ocassions were in the 500 yards of a drive after a good lay off, so no chance to warm up. Did 70+ miles in it yesterday before without any truoble. Taking it straight to my rover garage tomorrow morning but in the interim really worried ! have i bought a death trap ! Thanks Dan
DJ Brown

I've been told by the garage its the Gearbox !! ... nightmare. Has anyone got any other possible ideas ?
DJ Brown

I think suspicion should focus on the gearbox oil. Perhaps a simple change might improve things. I am no expert on this semi-auto, but I do recall reading about this elsewhere (look in archives), and this would be the simplest, cheapest problem to check out. And what gearbox wouldn't benefit from a change of oil from time to time? ;o)
Rob Bell

My 2002 TF Stepspeed had a simular problem, it was a 38 switch thats goes in the back of the gearbox.
Summit Motors at Maidenhead solved the problem
Good luck
J Watson

I would concur with JW. The gearbox is doing what it is told to do so find the sensor that is giving the wrong information.
Geoff F.
Geoff Farthing

Guys, thanks for your help so far. Also great help from CSMG and Owners Club. Had the computer diagnostics look on Friday, their T4 kept hanging reading the Car ECU. Could be their software version, mine software version etc
So we've changed the transmission fluid and I'll run this week but not hopeful this has resolved. Sounds more electical to me. ALSO the Clock (dash) does not keep time, the oil temperature (dash) bulb goes on and off......All looks like wires to me !
DJ Brown

It gets worse. The oil change has done nothing, all the correct ESSO High performance cvt fluid changed and it was not happy again this morning. I am now being told I could be confusing the juddering/acceleration lost with a misfire. I have a small coolant loss (couple of mill) and it could be getting in the cylinder bores. It had head gasket changed over 10k ago, so the documentation would lead me to believe. Am I looking at major surgery again?! if so , it will have to go back.
DJ Brown

If a misfire, loosing coolant at a slow rate, then I would suspect the inlet manifold gasket allowing coolant into cylinder 4.

Replacement is a bit of a pain, but a lot less involved than the head gasket!

I'd also be wondering about the sensors the chaps mention - might be worth checking out?
Rob Bell

Thanks Rob, I am going to try another t4 with B&G next week. Coolant loss is so minimal, but it does sound exactly that. I'll post any further results for future searches later ! thanks again
DJ Brown

Thanks - and fingers crossed! :o)
Rob Bell

back again, unfortunately the only way to tell if its the inlet manifold gasket is to replace it at 125+vat and hope, they won't know until they done the work......So I've been told - My trader doesn't want to pay on a whim, he wants a diagnosis. So likely the garage are going to say its the head !....
Trader then said he wants his own garage to do that, but he's talking about a skim and replace. I give up.
DJ Brown

I'm no expert with the MGF, but the symptoms you originally described do not sound like a misfire, not would a minor water leak (a few mill you said) into one cylinder cause that much of a misfire. The engine will pull on three cylinders. Especially as it's 'all or nothing' ie so bad that the engine will not raise itself above idle but, if you switch it off and then on again, it's fine.

Dare I say that you are prematurely heading down the head gasket / inlet manifold route when there are guys with Stepspeed transmissions saying that switch problems can casue symptoms like yours.

It certainly sounds like something computer-ish (switch it off and then on again), rather something mechanical. Particularly since your management system is messing with the Testbook...



I agree with Neil, electrical/sensor/ECU fault is the more likely cause. A wet plug not firing wouldn't reduce the engine to idle, that's happening as a reaction to an anomaly in sensor parameters. Hopefully the B&G TestBook will succeed in accessing the ECU and there'll be a conclusive error code, but the fact that previous connections have failed may indicate a faulty ECU, and when an ECU goes wonky a whole myriad of behaviours are possible. Hold off on the spanners and gaskets for now...

I agree with that too - checking the gearbox/ crank/cam sensors ought to be easy and cheap to sort out, so perhaps get them checked first.

Wouldn't explain the slow water loss though?
Rob Bell

Thanks guys, been the most useful post. B&G suggest if I dont get a reading we'll probably wipe the current ecu memory, try and download again, reprogram take it next step...
Just strange that its always after a lay-off, long idle time in cold (for example) - At train station just now,its been sat their all day. Turn on ignition, first time, no problems, car sounds nice. Don't drive off yet because i know I'll get an issue in approx 4-5minutes. If you sit and wait 2 minutes, the whole car suddenly roars up a bit starts to rock to the sounds of engine trying to do something and not quite making it, lights even flicker etc, dash, headlights, 2 minutes later , engine purring and you can take off. B&G are going to get it overnight so they can see symptoms i get now every morning. Have the symptoms change from the beginning , yes i think they have, because i think the new transmission fluid has helped stopped the some initial problems and maybe I had multiple to begin with (or just can't explain them very well!)
Kind Regards Dan
DJ Brown


Have B&G been able to identify the problem?

Tony Thompson

This thread was discussed between 25/10/2009 and 01/12/2009

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