Sputtering at midrange rpm somtimes

Perhaps I'm too late and too long winded! But to answer your question about the fuel pump, yes the pump failure mode could be gradual. But as for your "sputtering" engine the root cause could be related to the fuel or ignition system. For clarification I have a few questions. (1) Realizing this may be an intermitent problem, can you make the engine sputter if you rev the engine with tranmission in park? If yes, this reduces the probability of the sputter being ignition related. (2) When you do rev the engine do you get full rpm's (> 2000rpm) or does it seem choked/limited? If no, your suspisions maybe correct and your engine could have a fuel system problem. (3) Or possibly the sputter only occurs/worsens when the engine is loaded? You can sufficiently load the engine by applying the park, service brake pedal, shifting the transmission into drive, and then slowly applying moderate accelerator pedal. It shouldn't take more than 25 to 50% of accelerator application to safely load the engine.

Two possible solutions: If the engine sputters with the transmission in park or you just don't trust the fuel pump you might want to check the fuel filter first before condeming the pump. The alcohol content in fuel could have cleared enough debris to plug your 3 month old fuel filter. You should be able to blow through the filter without much effort. When the fuel filter is clogged it will fatigue the pump and can lead to failure. It could also be poor fuel quality though. (2) If the engine sputters loaded check the ignition coils and module. One way to check a coil is to disconnect a plug wire set before trying to duplicate the problem. If the engine sputters worsens with a wire set disconnected that coil is okay. You will find the culprit when the sputter doesn't change with a plug wire set dis connected.