My 1993 chevy luminagets lousy gas mileage,when it runs you smell

Chevrolet lumina euro have a catalitic converter Teena, Yes. Check the attached links, Good luck
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http://www.autopartswarehouse.com/shop_parts/catalytic_converter/chevy/lumina.html?redirect=1

RockAuto Parts Catalog

sounds like you have a vacum hose is off,

a good starting place,try rock auto.com, there you can get an idea of pricing.just put in your info. for the car and then you'll see there pricing.

sounds like a vaccume leak, like a dryrotted hose coming apart and the going back together

Black smoke is unburned gas. If the car is running fine besides the black smoke, it's most likely the Coolant Temperature Sensor. The part is roughly $20 and an easy fix.

PS- I'm guessing your check engine light is on...

Is yourd check engine light on? If it is, I would have the codes read first thing. If not, it could be clogged fuel filter or air filter, loose vacuum hose, or bad throttle position sensor or other sensor but the sensors or any electrical problem will set off check engine light.

if all the checks were done ! the pcm is bad

Computer. Or chip inside bad. its on passennger side under fuses

run hot even at highway speed? no leaks, or sweet smell? ever have to top off coolant? ever boils out of system? if no to all these, sounds like your cooling fans aren't working. there is a fuse either on the motor cradle or on the passanger side wheel well. start the car, let it warm up, and check for power to the cooling fans.

if you can check for spark when it wont start and fuel pressure and the service port , would be great information , otherwise pattern failure is ignition module and crank sensor (replace them as a set) , after cools off it will run again.