Ford Repair: Misfire #3 cylinder, haynes manual, vacuum hose

Question
Hello Brian,

I have a 2001 Ford Focus SE wagon, (8th digit) vin-3, DOHC Zetec 2.0L. This is Grandma's car, getting up in age and mileage, about 180K. It came to me for a tuneup, which I installed new plugs(platinum), wires(xact fit), air filter and fuel filter. It ran poorly so I scanned for codes, got P303 misfire #3 cylinder. I pulled both plug/wire off, checked wire with DVM and got 4 ohms for this new wire, which is in spec according to my Haynes manual. Reassembled plug/wire, still ran bad. Cleared code and reassembled wire/plug again. Same result.

Next I'm going to DVM the coil on the car, clean the pcv valve and anything else I can think of. I assume in the ignition there really is only those three items, but after some research I read about some Foci owners who have experienced a specific cylinder misfire and it was related to a vacuum hose somewhere around the rear of the head. I've looked all over the engine, but don't notice anything unusual. Have you heard of things causing misfires other than the usual culprits, i.e. plugs/wires/coil? What do you think my issue could be or what should I check for next?

Thanks very much for your time.

Answer
what kind of spark plugs did you install ??? this vehicle is very sensitive to only using motorcraft plugs. you can also move the spark plug from cylinder 3 to cylinder two and see if the skip moves to that cylinder also try this. follow the wires to the coil. spray the coil down with water and see if the skip gets worse. they were known for the coil to crack. please get back to me