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Good grief. Does anyone know what this thing is? It's funny, as much as I've had the hood open on this truck and one like it, years ago, I never paid any attention to this little canister. It's putting out air as the engine idles. Left side of the truck as you look at it from the front, just above and in front of the vacuum system coffee can.
Yep that is the output muffler for the air pump, right below it is the intake air filter for the same pump. Air flowing out of that muffler is normal if the air injection system is functioning correctly and the engine is fully warmed up.
Holy cow, learn something new every day. Thank you. Found a good video on YouTube on this, "EGR and Air Injection Systems Explained 1988 Ford F-150 5.0" or similar.
Those bypass valves (ABV) used to "fart" pretty loud when bypassing thermactor air to atmosphere
That is why they put the muffler on there for the later models
