Jim Grant's Tech Tips
Chevy S-10 Blazer, Distributor Problems
Q: I have an '88 Chevy Blazer, S10, 2 wheel
drive, 2.8l, with 168,000 miles. The maximum mileage I can get out of
my distributor cap and rotor is about 3,000 miles: Pulling the distributor
cap, I noticed burnt contacts on the distributor and rotor. After changing,
I am good for another 2,000 to 3,000 miles, before the engine starts to
run rough. The burnt distributor cap contacts seem about equal, the rotor
is the same, but with a leading edge burn. My spark plugs have a good
burn pattern. The vehicle starts the same way ever since I have owned
it, freshly tuned or not. Having replaced one bulb in 4 years (except
for the road damaged head lights) leaves me to believe, I do not have
an over voltage problem. I have no problem codes.
suspicions are that your distributor has gone "out of phase".
What does "out of phase" mean? Just under the distributor rotor
there is another component attached to the same distributor shaft. This
component is best described as a timer. The timer, in conjunction with
another sensor, provides the "time to fire the spark plug information"
to the ignition module. Timers have been known to loosen up and change
their position on the distributor shaft. The problem is the distributor
rotor position doesn't change and it will not be lined up correctly with
the contact area in the distributor cap. This condition requires more
electrical energy to jump the gap between the contacts. The result can
be accelerated erosion of the contacts until the wear is so great that
the engine will begin to run rough. The condition can be diagnosed with
an engine analyzer, but when it gets right down to the nuts and bolts,
a visual inspection of the components is necessary.