This article is from the Chrysler-Plymouth-Dodge FAQ, by Dr. David Zatz with numerous contributions by others.
Vaughn Smith's 2.5 was losing power and mileage. While replacing a burnt
rotor (one thing to look at), he took off the Hall effect sensor. He saw
that it read when each "vane" on the distributor shaft passed the pickup
point; the inner surface of the vane, though, was extremely dirty. He
replaced the rotor and cleaned the vane, and found that gas mileage and
power increased. He also found this problem on a 2.2 TBI and a 2.2 Turbo,
with some improvement in each case.