Hello. We have a 2001 Caravan (not Grand) SE with a 3.3l flex fuel engine. It has not been driving the best and has progressively gotten worse.
The issue is that the engine hesitates (not quite stalling), more of a bogging down at the top of the shift range during hard acceleration. It feels like it wants to shift (maybe around 3.8k?), but instead begins to hesitate and stays in gear. Backing off the pedal allows the shift to happen fine, once the RPMs back down to somewhere around 3k. It starts fine, idles fine and hasn't actually quit running. I did get a P0172 or P0174 (can't quite remember which) saying the fuel was lean. It also had 3 evap leak codes which haven't returned since I changed out the evap vent canister. (and cleared the codes). Also - it is generally REALLY BAD immediately after fueling up and I don't have to accelerate hard to get the hesitation. It smooths out in a few miles. Same thing when getting near a 1/4 tank.
Its definitely NOT the transmission slipping. I rebuilt a 4L60e last year and am quite familiar with a slipping tranny. My wife believes it started sometime after running out of gas (actually my fault) - so I started with the fuel system. Fuel pressure at the rail holds at 61 psi while running and quickly drops to 56/57 psi when shut off. Seems to hold this pressure fine, at least 20 minutes or better. I also replaced the fuel filter, added injector cleaner and tried new plugs and wires yesterday. I will say that the plugs looked like they had some excess carbon like the fuel was running rich (all 6) and gap was still good. Fuel economy seems to be less than it had been as well, although I have not confirmed this yet.
It was running better with the new plugs and wires, but the problem is still there. It tends to only happen in 2 and 3 gear, but I suspect that's just because I'm usually not accelerating that hard at takeoff. I haven't added any fuel to test that out again just yet, and it gets just as bad once in a blue moon without being topped off.
My next thought was replacing the o2 sensor to see if maybe the computer is compensating with too much fuel. Does this sound like a waste of money? I keep coming back to considering a new fuel pump because of the immediate change when filling up and I keep running into conflicting fuel pressure specs - my Chilton manual says it should be at 49 psi, but I seem to read online about it being 6-10 psi higher. Perhaps the fuel pressure regulator is pushing too hard?