Ford focus 1999 1.6 zetec, when engine heats up car idles erratic, engine nearly dies then comes good then nearly dies again. Tried cleaning out idle control valve was still the same so then replaced it and still the same. Have noticed when testing all this that the temperature gauge goes up and stays just left of half way and have had car idleing for long time and it never moves above that, but the cooling fans never come on, is there a chance that the temperature switch is faulty and could that be connected to the erattic idleing. Will probably change temp switch this weekend just in case, once i can find out where it is. Any help much appreciated.

check for any split pipes or connectors on the crankcase breathers,as this can give an uneven idle.

Ok thanks will check tomorrow again did a quick check before on all the vacuum pipes but what is the easiest way to check them, does a bit of fairy washing up liquid in a spray show any sign at all on air being sucked in or does that only work with air being blown out of the break.