I bought a 92 305 tbi firebird in January 2006, the car has been running great until it sat for about a month. At first it wouldnt start, but i replaced the battery and now it starts up just fine. My problem then turned into a carburator issue possibly, the car will start up and then it will idle rough then surge and almost shut off, when i rev the engine black smoke comes out of the exhaust, I can put it into drive and take off but it starts to hesitate. So far I have driven the car around town and it has been ok but it idles really rough ad sometimes shuts off. I sprayed some cleaner on the carb and injectors and I put some fuel injector and carb cleaner in the the gas tank. The strange thing is that 2 days ago it drove for a while and it ran great and then when I got home I shut it off and came back 20 mins later and started it up again and it was idling rough again and it was shutting off. Then this morning it started up great and then i drove it for 2-3 miles and it ran fine and idled perfectly. Im afraid that the problem is just going to keep coming back. Any suggestions?

 

Let me get this straight. You have a carb and a TBI unit on there???

 

Yes I do

 

they're mutually exclusive.