I just acquired a 1989 Dodge D100. This truck is the 3.9 L automatic. The codes displayed are 12, 23, 55. This truck was described as having a knock. I hear a lifter, but otherwise the truck pings badly. I was hoping for some ideas as to where to look to correct the issue. I know for the most part the computer sets the timing. It shows 38000 miles. Probably 138000 or more. I am thinking about the timing chain. Thank you.