Troubles with pressure

Hi, so totally a newb here. This is probably my third time using the pressure washer. The washer starts just fine then I noticed the washer would stall (I'm assuming cause I did not pull the trigger soon enough and there was too much pressure. So this kept happening so I decided to remove the unloader and see if the pin was moving freely and it was. I then adjusted the main nut and locked the nut. Stupidly I forgot to put the lock pin back in, turned it and the unloader shot out with bunch of water and this thing?. My unloader is kinda rusted btw. I put everything back together and it still stalls with to much pressure. Any help is appericate