Hello everyone,

I'm running a 1988 Ford F-250 with a good old fashioned gas-guzzling 460 7.5L engine. I just got my truck back from the shop, having the timing adjusted, ignition coil changed, and some new plugs installed since I lacked the tools to do most of it. I have very recently flushed and replaced the coolant and thermostat as well. It has a newish air filter (very clean, less than 5000 miles) and I noticed that the breather filter was liberally caked with dirt and oil so I replaced it.

My first question is what exactly does the breather filter do? It was pretty dirty. I have no idea how all of that engine oil got all over it. I realize that the breather filter hooks into the port where the oil is poured into the engine, but damn it sure was dirty.

Secondly, I noticed that my engine idles with a lot of sputtering occurring, especially when I come to a stop at a red light or something, even at normal or cooler operating temperature. I am aware that there seems to be a crack or leak of some kind up near or on the exhaust manifold. Would that have anything to do with it? I added some fuel injection cleaner earlier today as well. It got me wondering if the fuel throttle body might be dirty and need to be cleaned, or if the fuel pressure regulator could be stuck or just bad.

What is that breather filter for, and how might I stop the sputtering in my engine? Any and all help would be appreciated. I'm far from a professional!