90 Mazda 323 miss fire at acceleration in the middle of run on a slop. Sometimes stop when turn right at the top of slop. When gas is low, it stalls frequently. Refill the gas to full tank, it is not stall but still has miss fire. I have to refill after about every 3 gallons used. Checked plug, wire, distributor and rotor, it looks fine. need help please.