I just bought a '83 n/a zx and the engine runs strong and idles smooth, the only thing thats got me bothered is at idle and give it the juice, it hesitates for a second and sometimes you can hear a small backfire. I checked the cap and rotor, they look ok. I checked the plugs and they look ok....could it be the vacuum advance on the distributer lagging or is it something else worse. I can manually move the advance mech so I know its not stuck. Also I've noticed that when holding a speed, say 45 is seems to fluxuate like I'm moving the gas more and less. Its not much, but I notice it....then the other day I hit 73 and it did it real bad but not at 72 or 74....just right at 73 ????? The injectors make a clicking sound, is this normal or are they getting worn? According to the past records I got with the car, the injectors were replaced around 90K and it now has 148K. Could it be a bad fuel pump...I'd really rather not keep replacing things until it goes away. Any help to point in the right direction would be most helpful....