4age not starting - ae82 corolla gt

[4agepwr]

The starter motor is turning over, but the engine just isnt firing
Ive checked the spark and it is low
I checked the coil/ignitor and it seems fine because when i pulled the lead of the distributer cap and started the car it sparked quite alot.
All earth wires appear to be bolted down
Thought it might be the ecu, but not sure, I have started the car after this problem has occurred. It Can go fine some day then not start the next
What are some other causes of it not sparking efficiently?

[Caveman]

If the spark is good at coil then the path going to the motor is the leads, rotor, distributor cap, leads then spark plug. Check the cap and rotor for corrosion and bad contact. On an ae82 is its the original dizzy i'd say the rotor is well worn. The leads or spark plugs are the other things to check. The leads would be the most expensive thing to replace. Rotors, caps and spark plugs are cheap so i'd replace them anyway. Probably cost you about $100 for the lot brand new. If it makes no difference get a multimeter and check the impedence on the leads. It should have the rated impedence on the leads but generally it should be between 7-12k ohms (7 being the shortest, 12 being the longest).