Engine Size: 5.8L
Issue / Question:
High idle – changed the IAC valve three times, the last time I scraped and vacuumed out the carbon. Each time it runs great for 2-3 days, then the idle revs up really high. I turn the truck off, wait for a minute, and then turn it back on and it runs fine for a few minutes then idles high again.
It sounds like the ISC is trying to compensate for an intermittent vacuum leak. Its possible that the EGR valve is sticking open for carbon.
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