I have a 1977 Ford LTD with 289K miles. It has the 302 Windsor engine with a 2 barrel (motorcraft 2150). When I get the engine warmed up, it will start to misfire really badly. The idle will get very low when I put it in gear and it will sometimes stall. I checked the fuel pump, and its pumping plenty of fuel (It is a mechanical fuel pump). The choke is opening all the way when warmed up. I re-adjusted the fuel mixture screws, and it made it only slightly better, but the problem is not completely fixed. I'm thinking the carburetor needs a rebuild, but I had a mechanic rebuild it a couple years ago, so I don't see how it could need another rebuild. I need someone to tell me whats going on. Thanks.
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I have a car with the same carb. Check for vacuum leaks, 1970s vehicles tend to have a lot of vacuum lines and gadgets that deteriorate. When the engine is cold the choke is closed and may be masking the problem. One thing that frequently gets overlooked when rebuilding an old carb is throttle shaft wear which permits unmetered air to enter the intake. There are bushing kits available to fix this.
Also check your ignition system, that car would have Ford's Duraspark II ignition system. Obvious things would be the condition of the cap, rotor, and wires. It's also possible for the ignition controller box and/or the pickup in the distributor to flake out when they heat up.
Examine the spark plugs. If it's a misfire due to failing ignition, some plugs would look wet with gas or carbon fouled due to unburned fuel.
