Friend,
The symptom may have more than a single cause. The CEL is on because the O2 sensor voltages may be out of range. Until the 1988 California emissions version of CIS-E the CEL was merely an oxygen sensor malfunction indicator light. The fact that the light goes on and off makes me tend to agree that the o2 sensor may be defective or the mixture so very lean as to inhibit the voltage output of the sensor. Procure a 3mm allen wrench and muster up the courage to twist the 3 mm allen screw in the short little tower under the air cleaner. I would rotate the screw in a clockwise direction no more than 90 degrees at first. See if that doesn't help. It's cheap. "You can do eet"
Call us in the morning if that medicine does'nt help. You can always turn the adjustment back to where you started.
Don

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When the people fear the government, that is tyranny. When the government fears the people, that is liberty. -- Thomas Jefferson