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I have a 1996 Ford Ranger 2.3L with 190,000 miles. I recently did a head gasket replacement due to misfires and very low compression in cylinders 3 and 4. The truck had almost no power and there was a confirmed tear in the head gasket between cylinders 3,4. There were also big cracks in the valve seats so I replaced the head with a brand-new one. after the rebuild, the engine runs great. I have good power but now I have a high idle and fault code p1506. The engine now idles at 1100 rpm and if you rev the engine it will stay at around 1500 for a while before dropping back down to 1100. Here is some information I am receiving when using live data on my scanner. The IAC Valve is at 8% when idling, TPV is at .9, Long-term fuel trim is at 10-11%, and the desired rpm is 788, and no IAC fault, when using the scanner to higher and lower the IAC % from 0-10-20 the engine rpm does not move from 1100. The IAC valve itself is confirmed good, the PCV valve is good, compression on the engine is good. There is a continuous misfire in cylinder 4, the engine does not run shakey it runs well. the truck has new spark plugs and ignition coils. I cannot figure out how to fix this problem please help by giving any advice, Thank you guys.
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