Your timing belt has probably worn out, or broken, and has jumped timing.
If your Focus has "jumped time," you need to move the timing distributor by going back or forward a notch (or whatever) on the timing belt, without moving anything else. Better done by a mechanic. PrecisionTune seems to have the fairest prices.
The Ford Focus 2.0L has a timing chain.
Timing CHAIN ( 2011 Ford Focus 2.0 liter )
The 2008 Ford Focus has a timing chain, not a timing belt. The Focus has used a timing chain sense 2005. Timing chains are designed to last the life of the engine.
A 2007 Ford Focus , 2.0 and 2.3 engines , have a timing CHAIN
Timing BELT ( for the 2.0 liter SOHC and DOHC engines used in a 2002 Ford Focus )
The 2.0 litre four cylinder engines used in a 2010 Ford Focus have a timing CHAIN
The 2.0 liter engine in a 2005 Ford Focus has a timing CHAIN Helpfull
No , both the 2.0 and 2.3 liter engines in a 2005 Ford Focus have a timing CHAIN
timing CHAIN
It has a timing chain.