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running lean, code 172, and vacuum leak
The vacuum leak is in the back of the EGR valve. The valve stem is leaking on the fresh air side. Is this why my mileage is so good? If I replace the EGR valve will my mileage go down? I don't think it is dangerously lean, just enough so the 02 sensor doesn't switch a lot. I remember a thread a while back about unmetered air...guess now I get to experiment.
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1991 F-250:
4.9L, Mazda 5 speed, 4.10 10.25" rear
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