98 3.8L auto tranny with 122k

I bought car with PO saying the engine was seized. I removed all the plugs in hopes of getting the engine to turn with a breaker bar to see just how hard it is to rotate. What I have found is the engine will turn over really easy several times by hand but occassionally, it stops dead. I can turn it backwards just a little, then forward and it rotates easily again. like something is catching on the inside of the engine.(yes, I know, not suppose to turn one backwards). Not sure if it is hanging up in the lower end or the upper end. What could cause it to stop rotating after it has been rotated at least 3 complete turns. I am thinking maybe a bad rod bearing allowing the rod to hang up on the bottom of cylinder but not sure.

 

Sounds like a spun rod or main bearing to me. The bearing wedge together and when you back them off they un-wedge. I would not spend a bunch of time trying to figure out exactly whats wrong. This falls under all "roads lead to the same place". Either complete rebuild (most likely not worth it) or and used low miles long block.

When a engine spins a bearing what happens in the next few seconds determins the fate of the motor. If its not turn high RPMs and its shut down almost instantly it may be salvagable, But if it spins at 5500 RPMs or the guy "Just trys to make it" somewhere the motor is a total. The reason being is the spun bearing will cut off oil supply to its piston and in a matter of second the piston walls are being damaged. Also metal debris is being pushed into oil passages of the motor getting into all the wrong places. If you want to rebuild the motor its a lot less headaches to buy a high miles long block and rebuild that then it is to fix one that has come a part.

 

I would have to agree.... I dont know what sort of room you have in the newer cars but i have in the past jacked to motor and dropped the oil pan and swapped out whatever bearings were bad for a quick cheap fix .... I know in the newer cars most likely you drop everything out from the bottom but if you can get the oil pan off you can replace the bad bearing.... flush the motor several times to try to remove any metal particles there may be... but even thats not a quarentee you got everything .... but still, a few bucks and some elbow grease and you MAY have a salvageable motor .... At least before you spend the money for a rebuild

 

To get the oil pan off you have to essentially pull the engine out, not a little task on these cars. If it spun a bearing, then like gorn said it may or may not be ruined. Besides the possibility of killing the cylinder walls, there's also the chance that the crank and a rod may be toast.