This article is from the Chrysler-Plymouth-Dodge FAQ, by Dr. David Zatz with numerous contributions by others.
My 1992 Dakota 3.9L needed a new timing chain and gears
at 49,000 miles. This was originally diagnosed as "mis-phased"
distributer, and "fixed" to some degree.
According to one of the service managers, the 1992 Magnums had a
"single roller" roller chain. The 93+ engines have the more typical
double roller. This may be a common problem for the pre-93s.
The misfiring had been happening sometimes on upshifts, but worsened as
performance sagged. The misfiring occurs when the rotor gets enough out
of phase that the spark gets fed to the wrong cylinder. Ignition timing is
not changed by this
problem, valve timing *is*,
and distributer rotor "phase" is. Get it fixed SOON. (Ron Luse)