Weird idle, air-con thingy...

[chelvdog]

Hi I'm new here & have just bought my first e-series, an ED falcon. The car is in decent condition but has this annoying problem. occassionally on idle it is a tad rough and when I turn the air-con on, it seems to idle excessively high. I haven't got a tacho coz it's a GLi, but my guess is about 1500rpm. I prefer to do all my tuning and servicing myself, but could it be a faulty ecu? Btw, its my first fuel injected, ecu car! I'm use to Holleys & a timing light!