i just bought a nice 1998 dodge avenger balcked out,automatic,leather moon roof all that stuff

it drove great and then after i bought it it barley made it home it wouldnt shift gears it was basicly in limp mode,and as i got within my driveway it stalled and shut off,i let it cool and hours later i went to drive it again,it did fine but as i came back home the transmission did the same and there was a loud knocking from the eninge,and when i got home it yet,stalled again. THis morning i went outside and it cranked rite up but theres now an upper knock behind the first valve cover at the front of the car where it says 2.5L V6. you can feel it knocking right behind the valve cover,theres no doubt it an upper knock in the top behind the valve cover.

Now what could it be exacly? can it be fixed? the rest of the motor seems fine,coult some cams be worn out?,could somthing have come loose?. im normally a jeep guy and only woked or 4.0 6cyls so this is all new to me
and ideas guys? i really love this car and for the condition and price i got ift for is a great deal even if i have to fix it.

please give me some ideas thanks!

 

First check the TIMING belt , If it jumps 1 or 2 teeth it can damage the valves and cause bent valves

 

Also check for oil circulation in the head remove the oil cap and see if there is plenty of oil in the head you could have plugged passages