Hi guys, my EF has a vibration at cruzing speed, it's not severe, bit definitely there. It seem to happen when the engine is cruzing along at say 80km and low rpm & it's intermitent but at regualr intervals-1 second on, 1 second off almoste exactly as I cruze along. I don't have enough knowlege to diagnose. Could it be harmonic balancer? It's 6cyl auto and has done 240k.

Vibration could be any number of things. Wheel balance, bearings, tailshaft and as you mentioned, harmonic balancer.
What I would suggest is bring the engine up to cruise rpm in park and see if the vibration is present. If so you've just ruled out wheels and tailshaft. If not, jack each wheel up in turn and spin them by hand, any rumbling sounds or looseness in the wheel indicates wheel bearings. As for the tailshaft being out of balance, most often you'd feel the vibration through the body of the car rather that from the front.
Hope this helps you out.

thanks mate for your help