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Shuddering Bronco II

When my 1989 Bronco II has about a quarter tank of gas left, it begins to “shudder” and lose about 500 rpms while I’ve got my foot on the gas. It will shudder and lose power for a second or two, then run fine for a minute or so, then do the shuddering stuff again. It’ll do this all the way to the gas station. But with the tank full (or even half full) the shuddering stuff is gone as I drive out the gas station.
Any guesses on what this might be would be appreciated.
Adam

I’m guessing either the fuel pump is giving up the ghost, or something is clogging up the tank venting system.

One more idea: There could be debris in the tank (possibly from a tank of bad gas you got one filling) that is clogging the pump too. When the tank is full the debris floats around, but when the tank gets close to empty, all the debris is concentrated near the pump inlet and clogs it. If this is the case, you’d notice this more if you goose the engine, i.e accelerate, as this requires more gas to flow.