I have a 94 s10 vin Z 4.3L 4X4 5 SPeed in my vehicle fleet.
this problem may be a plugged cat converter. poor start, poor mpg, dies when driving.
does the engine run with no smoke out the exhaust ? if this burns alot of oil this would foul the plugs badly. use a hotter plug.
the distributor can get damaged from the windshield washer hose leaking, squirting on it. the coil connections need cleaning. use dielectric grease on the plug wire /distributor boots inside the boot.
plug wires need be routed correctly use tyraps/plastic ties to secure plug wires .
if the starter cranks the engine good don't mess with it. this is not an easy thing to mess with ///motor mounts and etc....
disconnect the battery connections and make sure the starter wires and other fastener hardware is all tight/clean with a wire brush the battery/cable connections till clean..
make sure the alternator is charging the battery . use a volt meter should get 14volts..if less than 13volts its not working correctly. make sure the small wire to the back of the alternator is clean and secure.
check the ground connections, if rusted remove and wire brush the metal reinstall.
remove the upstream O2 sensor leave hole open and see if it runs better. if so then the cat converter is plugged most likely or a restricted damaged muffler possibly.
this has a steel fuel tank replace the fuel filter.
the 5 speed manual uses synchromesh manual transmission fluid. do not use other fluids as this is the best correct fluid.
the leaking may be from the shifter gasket on top of the transmission . the shift boot removed this can be sealed.
that will keep you busy for a while !