2003 Jeep Liberty skips/jerks

Hey yall, I just bought a 2003 Jeep Liberty sport
6cyl 4wd with about 196k miles on it about 2
weeks ago. Seller told me there was a skip but i
didn't think it be much of a problem. When i go
uphill or try going 50mph it starts to skip/jerk. The
check engine light comes on and starts to blink. I
got it checked at AutoZone and the codes read
multiple cylinder misfires. The guys there told me
to get spark plugs and ignition coils and i did. I
changed all 6 plugs and coils and cleared the code.
The next day it comes on and started doing the
same thing. I got it checked again and it read the
same thing. Any ideas whats going on? Please
help.