This morning I started the 54 Packard Cavalier to drive it to work and it made a trip around the block running normal and then the engine started to stumble and not rev up.
Could have been accumulated water in the gas as Kansasboy suggested. The run around the block could have used up the uncontaminated gas in the fuel line, and started pulling water out of the tank.
There were three different scenarios when my cars would run OK for a mile or two from initial start, then stumble:
-automatic choke comes off too soon and mixture leans out
-carb ices up and richens mixture too much....I'll assume carb icing isn't a problem in Phoenix in September
-automatic choke sticks closed and does not come off, richening mixture too much.
If the gas isn't contaminated, my first guess would be a sticking automatic choke. When it died, did you notice if the choke was open or closed? Is there a lot of soot in the exhaust pipe?
Sticks in my mind if the mixture was too lean, the engine would rev OK in neutral, but wouldn't pull under load. If the choke was stuck closed, it wouldn't rev under any conditons because it couldn't get air.
If the engine is running too lean, it might be more prone to pinging, because combustion temps are higher. If too rich, it might backfire.
The engine in this video sounds to me like it's running too rich at idle. It stumbles and backfires. When the guys crank up the throttle they blow out the excess gas and it runs smoothly until it starts to load up again.
http://www.youtube.com/watch?v=tuMvqp7fWUU
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