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Help Please! Excessively high idle speed on 1988 F150

I hope someone out there has a solution for me. After driving (from a cold start) for about 20 -25 minutes with the heater & lights on, the engine switches into a very high RPM and stays there. This is hard on gas, brakes, transmission & probably more. I can correct the problem by turning the engine off for a couple of minutes. When I restart it the RPM stays normal. The problem is that on my hour long commute to work in heavy traffic, it is not safe to turn the engine off. So far I have tried replacing the Idle Air Valve, disconnecting the air conditioning, and pulling out the Cruise Control fuse. None of these have worked. My mechanic wants to "try" replacing the Throttle Body next. Before I go this route, does anyone out there have any other ideas? Thanks

Reply to
Robert
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Reply to
Chuck

The 302's are notorious for large intake manifold leaks, which result in a high idle. Since yours is intermittent, I'm not sure if that's an option. It really helped mine, though, when I replaced the gasket between the upper and lower manifolds.

Reply to
Joe

your small exhaust cross over tube is probably leaking and causing to truch to run fast.There is also the possibility you have a vaccuum leak, but I assume you mrch. has checked this!!

Reply to
Richard Powers

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