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Not the most exciting thread I know, but I'm at a loss here..
06 plate MK2 Focus, 1.6 vct petrol engine, engine light came on in January along with an intermittent judder under load and misfiring when idle. Fault code P2303 Replaced the coil pack and the problem completely went away for 2000 miles before reoccuring. This time the coil pack was replaced under warranty along with spark plugs and leads being replaced at the time.
Now the same has happened again, 2000 miles and eml is back on along with the misfiring. I guess the question is whether it's likely the garage has used a dodgy brand and an oem spec one would resolve the issue, or there's an issue elsewhere that's causing the failures.
There was signs of water ingress in the plugs back in January but checked a couple of times since and they've been dry. No other fault codes present. Googling doesn't reveal too much on the issue, except ecm damage caused by the failed coil pack or water ingress/corroded leads causing the failures.
Anyone had similar or got any pointers to rule out root causes?
Is the miss fire cylinder specific? Does it have individual coils for each plug (thats usually the way they work these days)?
Swap the coils around and see if the miss fire follows the coil or if it stays behind. If it moves then its the coil, if it doesn't then chances are its a mechanical issue of some sort.
Sounds like the behaviour of my 06 focus and it turned out to be a failed spark plug. The tip had fallen to bits.
Long time since I had my 02 Focus but I replaced the coil several times. It was a single block but twin circuit coil design.
But later engines may be different - many are ‘coil-on-plug’
What type of coil do you have OP?
Use proper motorcaft plugs n good leads
Plug gaps huge coil needs all the help it can get...
The genuine ford ht leads are astronomically expensive (for ht leads) , the coil isn't cheap either so might be something the garage cheaper out on as you say. It was about 75 for the coil and 100 for leads! In the end I got the lot from a scrappy so i could at least isolate the problem before buying new bits.
Is that the focus model where water leaks from the washer jets onto the cylinder head shorting out the plugs?