timing issuses

[parkrangerjeremy]

i been having poor fuel economy,overheating issues, and sluggish acceleration. i have no check engine light or nothin all my fuel trims look fine o2's are cycling correctly... i check live data on it and it show my timing at 16 degrees what could cause timing to retard like this??? Its a 1993 4.0 manual

 

[xgenralxleex01x]

mines doing the same thing buts a 90 4.0 auto.

 

[Rifleman]

Worn spark plugs will causing timing to retard due to their typical late detonation. Pull the plugs and inspect the ground electrodes for wear.

 

[parkrangerjeremy]

they are new but look a little white and look like its running lean which could be from the timing retarding.... i just put a new coil pack on it also from a parts truck i have laying around but didnt help at all