1999 Toyota Avalon Question: as Im driving my car wants to pull to the left; what causes this problem?

Pulling to left or right is an indication that the alignment is out of spec. You will need to get an alignment as soon as you can or risk wearing the tire edges out very quickly and then need tires too.

You or your mechanic will need to inspect all front and rear suspension parts and make sure they aren't broken or severely worn. For about 60 bucks you can get a chassis alignment done at a local repair shop that should restore correct alignment to your vehicle meaning it won't pull to the right or to the left. Make sure your tires are wearing evenly and struts aren't leaking or you may have to replace your vehicles struts. I do all this myself. If you have any more questions my name is Austin and I'm an armature mechanic not my main job. Just a hobby. toaustin@hotmail.com is my e mail address I will be glad to help free of charge.