1997 Camry I4 - Pulsating hesitation uphill and downhill

[bobjava]

I'm having a weird hesitation problem that doesn't seem to fit problems described in other threads.

The car is a 1997 LE 4 cylinder with 189k and an automatic transmission. I was taking it over the Grapevine on the way to LA yesterday and noticed a strange hesitation (engine or fuel?) when the car was at a significant incline or decline. You could feel pulsating hesitations (on, off, on off) spaced less than a second apart.

It seemed to occur when I was only partially into the throttle. If I gave more gas, the problem disappeared. I've never experienced this on flat land or lesser inclines/declines.

My first thought (and hope) is that it might just be the fuel filter. I know it could be a several other things (cap/rotor, plugs, wires, throttle body), but does the narrowness of the circumstance indicate one over the other? I don't want to throw money at everything if I can help it.

EDIT: The car had about half a tank a gas at the time this occurred.

[Mister_Perkins]

I would suggest doing a standard Tune-up (plugs, wires, fuel filter, air filter) if you havent done it in a while .. Also run some fuel system cleaner in it, and check out the TPS and make sure its running right.