2002 ford focus rough idle when at operating temp.

car has 85000 km and is equiped with spi engine.engine works fine under load and idles fine when cold.any ideas?thanks.....AndyS

Did you check the pcv line?

Vacuum leak in the intake system or the vacuum hose going to the elbow in the top of the engine. The elbow is known to splilt or get a hole in it. Check for characteristic whistling of a vacuum leak.