Ok the past 2 days have been annoying

ok heres the prob my 240 which has a fully rebulit ka motor in it is not holding idle very well .....if i sit at a light is just sputters then dies after a min or two unless i put it in neutral ....and a loss of power....now i have asked people and seems like its a spark plug or a cloged fuel injecter

i thought id ask you guys on tr b4 i make a trip to autozone