Ford Focus Misfire

I posted a message a while ago about a 1999 Ford Focus 1.6 Zetec with an intermittent misfiring problem.
The misfire usually occurs during acceleration in 4th or 5th gear or
when accelerating hard in lower gears. Most of the time the engine idles fine however on two occasions the misfiring has been pretty severe and the engine has stalled whilst idling.
Two seperate garages have looked at the car (one a Ford Dealer) and no obvious problem has been found by diagnostics. The confusing thing is that when the plugs and coil were changed, the problem disappeared completely for a while but returned very slowly.
It seems as though there is a problem which is having a go at the ignition system. Any ideas? Anyone had a similar problem?
Thanks for any words of wisdom!
Andrew
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. Cheers
Kaiser
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Kaiser wrote:

I think your problem is different. Your fault is a very common early Focus one. It is caused by progressive failure of the Vehicle Speed Sensor. If you search in this NG using Google Groups you will find loads of info to help you.
HTH
Chris.
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.

I've found the thread. I can now begin to get it sorted. It's a real pain.
Kaiser
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This may be the same problem i was haven, I though it was a misfire, and though it was the EGR was gloged. Very confusen. It would run great some times, and other times run like shit. Stalling out. burning fuel ( smell from the cat) so i figured it was a bad spark plug. Well i got to work and it cut off on me. So i started up and messing around the hood.. and well the
""Postive Battery cable"" was well in another word shitty.
It was arching and metaling the battery little by little, so i replace the Terminal end and walla its good. Check the negative as well.. there are recalls on them
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Andrew,
I assume you changed your high tension wires. I saw this problem in a Miata and like most cars, it has the plugs deep in the head and a long wire to get to it. In this case, you could see where the spark was jumping through the plastic insulator and to the head. New wires cured it in this car. It sounds like the problems is in your secondary ignition system and when you need the power, the voltage isn't there. An ignition scope may help you but I would start with new plugs and wires. Make sure ther wires are fully on the plugs too. It sounds like ignition vs fuel and I would think that a fuel injection problem - too lean mixture to fire under heavy load - would set a check engine light but maybe not.
Gary
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Andrew: Im having same symptoms.2000FF with 80K miles. yes I changed wires and plugs and have had all recall work done.Am waiting to stall out,have come close.Computer diagnosis is negative.
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