I have a 2008 fiesta 1.4 zetec climate which has recently started to misfire on idle. No warning lights are showing and ford say they can't find a fault but I'm not imagining it. friends have pointed it out when sat at traffic lights. seems to be worse when engine is warm. Any advice greatly appreciated. want to fix this problem as its happened at the wrong time. just before I sell the car to upgrade to a bigger one. Many Thanks

Lee_Ford2008, November 2014

The core plugs in the cylinder head can fail on these cars. When the engine warms up the cooling system pressurises and a fine spray of water exits the cracks in the core plug joint and soaks the spark plug causing a misfire.

If this has happened on your car then the cure is to replace the offending core plug with a new one. Clean up the mating surfaces before you fit the new one.

See:

http://www.honestjohn.co.uk/forum/post/index.htm?t=64138

http://www.fordownersclub.com/forums/topic/35697-leaking-cylinder-head-core-plugs/

http://howtomendit.com/answers.php?id=133391

ChicksFan, November 2014

It is difficult to say what your problem is, you don`t say what the workshop checked or did but plugs, leads and coil packs would be worth checking out and also a compression test may be worth a go, good luck

cdc, November 2014