something burning while warming up

i have a 94 lumina. In the mornings before i go to work i go warms up my car and turn on the heat while i get ready to go to work. when i come back i get inside and there is this burn smell i first thought it was something to do with the heat so the next day i only turned it on before i left for work i open the hood and the smell was present. i also notice while changing the crankshaft sensor that there was oil leaking somewhere back there but i never notice any on my driveway.

only leaks @ crusing rpm. Check PCV valve make sure that it operates freely. If not, replace it. Also make sure that rocker arm covers are snugged down properly.

k ty for the reply ill check this weekend and post on what i find

If it smelled like warm antifreeze it could be your heater core.