If you are doing ground-runs or air-tests after work has been done on the engine or FCU - check that the throttle position indicator on the FCU (the arm in the green / amber / red arc) is actually in the closed position when the throttle lever is closed.
I had an incident where the throttle was mis-rigged so that when the throttle on the collective was fully closed - the FCU was still slightly open - It lit off at about 7%N1 (before i had opened the throttle lever) and i had to use the shut off valve to cut the fuel. Not pretty!
OH