Driver Side Door Lock

Ok i purchased this 2002 Sunfire in August and when i bought it the driver side door was tricky to unlock from the outside with the key (no automatic locks) So it is now November and it will not unlock at all. It is not the key because it works in the passanger side lock just fine along with the trunk. I asked a mechanic and he said to put a crap load of lube in it and it should work. I did and it worked for about a day. The next day when it stopped working again i put more in and it will not work at all. Does anyone have any idea what could be wrong... And how to fix it?

Thanks

I've got the same problem with my 04 sunfire right now with auto locks.

It doesn't like the cold weather for some reason. When temps are above 40's it works fine, but in the 30's it never unlocks right away. What are you lubing it with? I would suggest some graphite. I have just been too lazy to do anything since I drive my car maybe 6 times a month while at college.

Sounds like that cylinder needs replaced. Could be a problem with the lock rods as well. I would suggest removing the door panel and examining it from the inside. Disconnect the lock cylinder and see if you can unlock the door with the lock rod. If that goes smoothly it would be a pretty good indication you need a new cylinder.