HELP 1994 grand am

:banghead: OK here is the deal. My car started spitting black smoke, choking with hesitation, and lost about 70% of its gas mileage. Took her to the doctor. He put in a new computer which was not needed, a new O2 sensor which was needed, fixed a ground, and replaced the fuel filter. Worked great for 1 1/2 weeks. Cost almost $900 still owe $300. :2cents: Well, 3 days ago it all started up again. Obviously I am not going back to the same mechanic and I guess I will just have to take the time to do it my self. So now the question is what is the problem? I am thinking that a fuel line could be clogged?? Any other Ideas and if it is how on earth would I go about unclogging it? PLEASE help!!! :1zhelp:

there are actually 3 o2 sensors on the 3.1 v6, one on the front manifold, one on the back manifold, and one on the cat conv. so the mechanic should have done them all or none at all! Go back to the same mechanic and call him on the fact taht he ripped you off, and demand that he fix the problem. If he charged you $900 then that car should be running right. Also, sounds like it may be the cat, b/c when the o2 sensors are bad the cat can go.

I am having a simmilar problem occuring maybe once every 2 weeks or so with my 94 ga but i havent fixed it yet b/c its not too bad yet

My 94 GA is a quad 4. So do I still have 3 O2 sensors or does that change it to just the one? :newbie: I know some things but I am definately green under the collar on this particular area? Thanks for any input that you have!

the quad four only has one oxygen sensor