I am going to need a new car soon and I was curious if I can borrow against my IRA to pay for the majority of the car so I don't have to finance much. Also, can I borrow against my IRA to pay off debt. What are the advantages and disadvantages of doing this?
No. Borrowing is not allowed, but if you take a withdrawal, you have 60 days to deposit into another IRA account. This effectively creates a 60 day loan. Not what you're really looking for.
If you take this withdrawal and re-deposit to new account within 60 days, no problem. If not, you owe tax on the untaxed amount as well as a 10% penalty. This comes from IRS' Publication 590, I have the document memorized by substance, not page number.