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cylinder misfire, please help


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Hello, I will try to explain as best I can, I don't know anything about cars and only passed my test 5 months ago.

Bought a 2005 fiesta style in January. Didn't drive it too much as was nervous, gradually started driving more, mid February the engine light flashed a couple times when driving, mainly on hills and there was a loss of power. Googling answers told me to change spark plugs, so my brother and dad did that for me and found the spark plug wells full of water, car ran really nicely for about 2 weeks. Engine light started flashing again, same sort of thing only on hills or on the flat when going between 2nd and 3rd gear. 

Engine light then stayed on, borrowed a code reader. Got a P0304 code showing a cylinder 4 misfire. Took the top off and the 3rd and 4th spark plug wells are full of water again. Dried it all out yesterday, put the top back on, drove home. Could barely pull away in 1st gear at times, quite juddery and not very happy when driving, engine light flashing. Then showed 2 codes as P0304 and P0300 - showing cylinder 4 and multiple cylinder misfires.

Took the top off again today, the spark plug wells 3 and 4 very slightly damp but not full of water, all the leads fitted properly. Drove nicely for 10 minutes when it started all over again, engine light flashing, barely moving in 1st gear when trying to pull away, loss of power especially on hills.


I am googling and I am getting so many different things I don't know what to do. Most common seems to be coil pack and leads, and if I do this may as well do new spark plugs again in case the water has affected them.From the old history the spark plugs were replaced 2 years ago and when they came out in February for new ones again, they were rusty.

The water getting in is obviously an issue, but today the engine light was still flashing even though we dried the water out? I can't see how the water is getting in there as its under a plastic engine cover. I know from googling the washer jets can leak but we have checked them and there is no leak. Have poured water across the windscreen and water runs down the windscreen wiper motor in the middle of the windscreen, so could it be that rain is getting in some how?


I am trying to sell the car as I am getting a family members car but I can't sell it as it is, and don't know where to start to try and fix it.


Any advice please :(




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you say the washer jets aren't leaking, how do you know for sure? The plastic engine cover you mention is the air filter which sits on top of the engine. Look at it and see if it has any dried water marks on the top at the rear at either side as when the jets leak (or even if rain water is finding its way under the bonnet from the windscreen) it drops onto the rear of the air filter housing and drips/runs down the back into the recess on the cam cover. The water could also be from corroded core plugs which you would know if the water had a colour to it or had a smell of anti freeze. 

Easiest thing first is to replace plugs/leads/coil (as it sounds like they've gone) and a 10 minute job to remove and seal the jets with a little silicon then put some silicon on the underside of the jets from under the bonnet. Then you can rule the jets out. Had the same problem on my 2004 fiesta and sealing the jets cured it. (I never saw water in the ports but I did see water marks on the air filter housing)

'if' it persists after sealing the jets then I'd be looking at leaking coolant from the core plugs which you might be able to see by looking down the opening for the the spark plugs (after drying the ports out) , see if the core plugs are badly corroded. If it's the core plugs then you have a slightly bigger job on your hands to replace them.

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