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MG MGF Technical - MGF VVC misfiring. Please help!

Over the last few days, my year 2000 MGF VVC has been misfiring. when I am travelling at maybe 30mph in 3rd gear and then accelerate it occasionaly judders until the revs pick up. The engine sounds fine at rest, but only does this when driving. Does anyone have any suggestions? Does it sound like an ignition or a fuel problem? The weather here has been very damp, could this be related? Any tips would be greatly received!
Peter
P Wilkinson


Could be a dodgy plug ! does it feel like its firing on 3?

When did you last change the plugs?

Stu
Wokingham
S.C. Dickens

Or needs new leads - not an uncommon problem on the VVC.

Ted
Ted Newman

I agree with the plug lead suggestion. Even if it's not the problem it appears that after 3 years or so the leads need changing.

I used B&G to supply silicone sports leads.

Brian

And finally it could be the coils
(I think that covers most the HT circuit ;-)

The coils in the VVC are located in the direct path of water pouring thru the boot vents, and have been known to break down- see the archives
Will Munns

Just as an aside, when did they start mounting the VVC coils on top of the plugs? Anyone know?

I would check out the plugs first as I had a similar problem some years ago and finally changed the plugs and checked the gaps to the minimum. From being a car that would not start on wet mornings it has never ever given problems starting since.

Bruce
Bruce Caldwell

I agree with dodgy plug or HT leads. Mine did the same and fine once new HT leads were fitted.

BUT get it checked quickly as if it is misfiring the engine will be ejected unburnt fuel through the exhaust system which can ignite in the catalyst and break the ceramic. Expensive

DJ
DJ

very much doubt it is the plug as they should last 60k,it is very likely to be the leads arching out. Is your car not covered by a 3 year warranty if it is get it into a dealership!
ricky

> very much doubt it is the plug as they should last 60k

Reading the box on a replacement set, they stated 30K or 3 years, so I suspect the 'F' rating's a bit on the exaggerated side.
Leigh

I would just like to thank all of the advice I have received from people on this board. I checked the plug gaps - they were fitted new in a major service last month (I requested them!) and they were set at 1,2mm to 1,3mm. I've reset them to 0.9mm as per the manual and hope this makes a difference. Also replaced the leads and WD40'd the HT area. I hope this cures it but I won't find out until the next downpour - which shouldn't be long living on the Isle of Man!
I'm a Design Engineer and I wasn't too impressed with the positioning of the coils on the back of the engine block, as Will mentioned, direct in line with any road spray coming off the drive shafts, etc. Also the top engine cover was an absolute sod to physically get back in, with the 3 forward bolts difficult to get at. I know there is not too much room in the engine bay but am convinced these problems could be designed out! Ah well, still love the look of my MGF, hope it's going to be reliable!
Again many thanks to all.
Peter
P Wilkinson

One of the penalties of having speakers in the T-Bar is getting at the engine cover bolts - no problems with my older *F*.

Ted
Ted Newman

I have had the same problem with my F, it seemed to 'misfire' when it was wet, it has been back to the garage repeatedly and had a new throttle body fitted, new plugs and new leads, still no joy,

The last time it went back they told me it could be where the fuel is being put into the engine there is an iris like arrangement which gets wider at higher revs to let in more fuel and when you slow down it gets smaller, they told me that the problem could be at slower speeds the iris may not have closed properly and has stuck fully open allowing in more fuel than the engine can burn causing the engine to choke,

I wont know if this is the problem until the 8th when the F goes back again!!!!

Hope this helps
R Crooks

This thread was discussed between 25/04/2003 and 30/04/2003

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