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MG MGF Technical - MGF judder

I'm looking to buy a P Reg (1996) MGF. It's only done 28k miles, so it's spent a lot of time sitting in the garage! The chap who is looking to sell to me uses it infrequently, and he bought it from his son-in-law who used it infrequently.

Anyway, I took it for a spin today, and I noticed a rather severe juddering when accelerating gently, especially in the low gears. It seemed to be less severe when accelerating hard, or when I got up into 4th and 5th.

I've looked on the web and read a few references to (what would appear, at face value, to be) the same problem, and a number of solutions appear to have been suggested, from changing the leads, plugs, rotar arm, etc, to unplugging the the throttle needle sensor, but these don't seem to have sorted the problem out.

Does anyone have a definitive answer to this problem? Everything else with the car seems to be fine.
Leslie Lawrenson

It sounds like a decent car Leslie; I can think of a childish workaround for the acceleration problem! However as the seller sounds friendly, can you not drive it for a week or two and see if it improves with(more enthusiastic)use?
C.R.B. Simeon

Hi! Leslie,

Where did the car originally come from. I'm thinking of the petrol contamination caused by Tesco/Morrisons
etc., selling duff petrol back in February of this
year which I think affected mainly the London area
and East Anglia. Caused similar sort of problems to
what you are describing, in which case you will need
to install a new oxygen sensor into the exhaust system, cost about £200 plus.

Regards

Bill Pearson
W.A. Pearson

Hi, peeps!

I have spoken to an MGB expert mechanic (he maintains my 1978 mgb roadster V8 conversion), and we've knocked this about today.

I'm going back tomorrow to do a few more tests. I'm going to take the car out for another drive, take her up to the point where the judder cuts in, and then knock her out of gear. If the judder continues, then I can rule out any problem with the transmission or the engine. Then, I'm going to rev her up in neutral to see if I can get the judder to repeat - if it doesn't, then we can rule out any problem with the fuel supply system.

It's likely, then, to be something to do with the wheels (tracking? balancing?) or the tyres. Given that the car has spent long periods parked up in a garage, it's likely that the tyres have flat-spotted, and I am told that this will cause the car to judder at lower speeds and on low revs, eventually evening out as the car picks up speed.

I'll let you know how I get on, as this might help others.
Leslie Lawrenson

An update!!

I took the MGF out for a spin (test drive), and the problem seems largely to have disappeared. It was present only in 3rd gear, and most prominent when dropping down from 4th and then accelerating back up again. When accelerating through the gears from 1st, the problem was hardly, if at all, noticeable. There is no fluttering of the needle, and the juddeer does not continue when the gears are disengaged, so I think we can rule out a transmission problem. Also, when the engine is revved in neutral the problem does not persist, so I don't think it's a fuel supply problem.

The seller tells me that the car recently flew through the MOT, so there are no emission problems, which would have indicated any problems with the throttle sensor or EDU. He tells me, also, that he recently replaced one of the tyres, but that three of them have been on the car since before the MOT before last.

I'm betting that the problem is to do with flat-spotted tyres, or something to do with the wheel balance.

Anyway, I've agreed to pay the chap £2500, which I think is a real steal, especially given that the car has covered only 28k miles.
Leslie Lawrenson

Chuck some reddex in the tank then an Italian tune up, followed by 4 wheel balance and tracking. Sounds like you have done really well there. :o)
C.R.B. Simeon

This thread was discussed between 28/05/2007 and 29/05/2007

MG MGF Technical index

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