William, Interesting theory. Watching my O2 sensor monitor gadget http://neksiwel.20m.com/photo5.html , I notice that rhythmic idle fluctuations correspond with changes in the output of the O2 sensor. On my truck, they are more noticeable while cruising slowly in first gear at idle speed and barely detectable just sitting at the light. You did not say how badly it was hunting. On our 85 I could cure this hunting my turning the idle bypass screw inward (CW). While we are throwing theories around, how about a bad chassis to engine ground strap? The extra current of the fan could be dropping a voltage across the poor connection which might add or subtract from the O2 sensors output. To test this theory I would turn on as may electrical consumers as possible and measure the voltage difference between the case of the alternator and chassis ground. Should be as close to zero as possible. My truck was loosing almost a volt here and I actually added a hefty wire between these two points. While you're at it, I would also measure the voltage drop between the positive battery terminal, if possible, and the output of the alternator. Some older Vanagons had an underrated wire between these two points. Ken Lewis http://neksiwel.20m.com/ |
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