m16 trigger malfunction

that m16 i picked up sat. i went out to test fire after cleaning and the trigger was hard to pull, was set to simi-auto, started firing full-auto. now when i flip selector switch to simi it starts firing full-auto without touching the trigger.i cleaned an lubed the barrel. and sprayed a little silicon lube on the piston spring and trigger when i cleaned it. i didn't do anything to the gearbox otherwise. i also taped up the wiring in the stock to protect it from wear. could the wires be touching somewhere? any ideas?

All I can honestly think of is either you got the switch put on backwards, you grounded a wire, or maybe someone has a more realistic answer, as I am clueless.

sound's like the trigger switch got stuck , you may need to open up the gear box , not an ez job

after posting i disconnected bat. pulled trigger couple times connected bat. now works fine. ??? if happens again i'll dig deeper.

Another possibility is the safety switch plate on the outside of the gear box, it is part control of semi, auto and safe.