egt sensor problem

[morris400]

ive spent all day trying to get the passenger side egt sensor put in, the threads on the sensor are fine, the threads in the mainfold look good, when i go to screw it in i can get 5 0r 6 turns by hand and only 2 with my wrench then it pops out. is there a chance the threads are not maching up? im not sure whats going on here. can i run the car with the sensor only a little bit in ? and is there another way or somthing i can use to get the sensor to stay in ? please help as i need the car for monday, thank you


ps the sensor im installing is a used one i got from the classifields AZ. on my old sensor the nut got mangled and there were no threads on it.