I am trying to help a freind of mine find a truck. We test drove a 99 yesturday and it didnt sound right. The best I can explain is instead of a diesel rattle or ping, it had more of a plunk, along with the rattle . Kinda sounded like one cylinder my have low compression or somthing. The truck had 140k. My first thought would be maybe it had a burnt valve. Any info?

 

retarded timing would sound less crisp.