I ve got a 2000 ford focus. I stop to run in the store. When I got back in the car & started it the. The motor started nockn & then died. After towing it home. I dropped the oil pan rotated the motor & didn't see nothing wrong whit rods or piston. When I pulled the spark plugs, the plug in the #3 cylander was broke. I put cheap new plugs in, & when I started it the the lifters in the head where nocking & then the car died. I toke off the timing cover & made shore the timing marks line up right. They did. So I need to know if there's any thing easle that may cause these problems. Before I pull the head off & get it fixed? Thank U