aaaaaaaaaaa D series and crank pulleys.. man my z6 has spit out its crank pulley so many times i lost count! the bolt just backs out and the pulley just drops.. my friend had the same problem and a stupid mechanic instead of putting some locktite on it, he put a bigger bolt that was not honda oem and fucked it up.. the pulley started wobbling and making a funny noice till it came off again.. now the crank was bad at this point but he needed a quick fix so we went to honda, bought a stock bolt put a bunch of red locktite allover the hole and the bolt and impacted it in, that way it stayed on and never came off again.. even do the pulley after that always wobbled a bit, it worked.. i put locktite on mine the last time it came off and it worked wonders! the engine blew and the pulley still solid.. hope this helps..

take the pulley out, inspected if there is nothing wrong buy a new bold (4$ @ honda) buy some locktite put some and impact it in.. and i promise no matter how hard u run ur car it wont come off.. only way to get it out is with a air wrench..