Sorry guys I havn't read your answers for this post sorry for that!

So, many of you are right I'm talking using a fault code reader (which should tell you if a sensor is dammaged).
I said 'should' because it can only tell you if the sensor (or loom) is cut or in short circuit and sometimes the ACT or the ECT are simply out of there range giving wrong informations to the ECU so you get wrong fuel and ignition timing! but it's the first thing to try anyway.

As I said somewere else another simple test to do is to check ACT and ECT sensors as they share the same kind of resitor, when the engine is cold you should get the same value in the two of them using an ohmeter! (about 3.0Kohm @25°C).

Back on the autodiag now.
I'm sure you should be able to find the complete stuff all of you need by becoming a Goldmenber and having a look to the "Technical essay Archives" section.
If you don't wan't to give 20£ for the forum contact me on MP and I'll see what I can do for you (the point is I don't have it in english...)
For information to built you own reader you just need an old type voltmeter (needle type) or a 12V led (led + 1Mohm resitor), a piece of wire and a paper clip!!!
That's why this test worth to be done

Just one final word about the T25 (small turbo cossie) as most of you knows the use the Ford ECCIV ECU then this test does't apply and you'll need to go to a Ford dealer to read the fault codes..