My 91 Chevy Lumina needs help!?

[KaylaH]

We took it to a shop and paid 90$ for them to plug it into the diagnostic computer. The only alert that came up was the O2 sensor. However, that wouldn't cause the problems it's having which are: Shuddering and backfiring when I accelerate, even without a load; dying frequently when i try to start it, back out, or drive at all (wasn't doing this until we got the oil changed. barely made it out of the shop's parking lot.); oil light sometimes comes on when I slow down to 20mpg or lower; Check engine light occasionally comes on.

HELP!!!!?!??!!!!

[ChrisH]

judging by the symtoms i would say that you may need to replace the catalytic convertor but if it was my car i would start with a tune up and go from there

[jnc623]

Sounds like the catalytic convertor is plugging up. the engine cannot get the exhaust out and it basically smothers it self. try taking the O2 sensor out and taking a short drive, see if the drivabilty problem gets better. If it does, you have your answer. A good tune-up would help tool.