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4kq surging improved

I found a way to reduce the 1,700 RPM surging on the 86 4kcsq. I increased
the sparkplug gaps to 0.040 inches. The surging is greatly reduced and only
faintly and randomly noticeable when I try to hold the car at 1,700 in
first gear, driving slowly along like I was looking at house numbers.

I had tried new plugs, a new cap and rotor, new wires, cleaning all the
grounds, and checking all the sensors/ECU inputs. Didn't do anything to
change the surging/bucking.

I tried changing the point gap to 0.025 inches and the surging became
bucking. Got much worse.  AHAH! Maybe a wider gap will do the reverse of
worse. Tried it and it worked.Tomorrow I will try a 0.045 gap, seeking the
limits of this fix.

Some of you will understand why it works.  I don't.  Fact: A wider gap
increases the resistance in the high voltage circuit? Maybe the spark is
bigger and fatter, and hotter?

Another data point: 1,700 RPM is where the centrifugal advance kicks in and
ups the timing. Maybe the centrifugal advance mechanism is gummed up and
working oddly. On Thursday I will take the distributor apart and check this
out. Why should I have to run exotic spark gaps to keep my engine running
nearly OK? I will stay with this problem until it is resolved in favor of a
smooth running engine.

Thanks to all the listers who gave me advice on this matter. It steered me
to the ignition system, and gave me the courage to keep trying.


Doyt Echelberger
86 4kq     better
87 5kcstq  does it get better than this?