glenlivet

Howdy All,
I'm new to the forum. I have a '99 Malibu 3.1L V6, "J" Code engine. It quit on me and would not restart and keep running. Had it towed home. The symptoms are: 1: Runs really rough. 2: Severe backfiring and pre-ignition which make it knock really bad. I hooked up the OBD reader and it shows no error codes. OH GREAT!!!! I did some poking around on Youtube and a few other forums and the replies to others with my same symptoms were that the engine had probably jumped timing owing to a bad timing chain. After going through all FUN of getting the timing chain cover off and checking the alignment of the timing marks, the marks line up. OH GREAT!!!! There is however, about 1/8" or better of slop in the chain on the return side. Is this enough to cause the engine to do this being that the problem came on so suddenly?
Anyone had the same problem? Any suggestions as to where to go/what to do/check next would be greatly appreciated.

As always, Thanks in advance.
Glenlivet
AKA Dan