How to set timing on 89 3 liter MPV?

My parents have an 89 6 cylinder MPV that's running quite poorly. Little power, hard on fuel and lots of spark rattle. I want to set the timing on it, but I don't know how to go about doing it. The underhood sticker refers to a diagnostic mode, but I don't know how to get this diagnostic mode. How do I do this? I want to do the timing so the van will run with thr transmission in economy mode without spark rattling like crazy.

My parents have an 89 6 cylinder MPV that's running quite poorly. Little power, hard on fuel and lots of spark rattle. I want to set the timing on it, but I don't know how to go about doing it. The underhood sticker refers to a diagnostic mode, but I don't know how to get this diagnostic mode. How do I do this? I want to do the timing so the van will run with thr transmission in economy mode without spark rattling like crazy.

As far as setting (adjusting) the timing... first you should have a Timing Light & RPM tools to check & adjust your timing...The rest will be based on repair manual for the specification adjustment & your weekend mechanic know how.....
Good luck.

uh yea drivers side eng bay their is a little box flip the top up and look in thier one of them will be labeled ten grd this to set your base timing and idle