Well for starters im new here, and so far i love this site and its very helpfull. well my problem is i had to replace my fuel pump on the 307, ever since i did my car boggs down at a light and starts blowing out black smoke, but it dont do it all the time. my baby has never did this until the new fuel pump. plus as soon as i take off it runs like it should...help.
Your description sounds like the typical leaking needle and seat in the carb. This can be related to the fuel pump replacement in a couple of ways. First, if you dislodged any crud or rubber particles from the hoses while changing the pump, that crud may have lodged in the carb and is preventing the needle and seat from closing completely. This can result in a higher than spec fuel level in the float bowl and will result in the car running very rich and bogging down at idle. Once you step on the throttle, you're using fuel at a higher rate and thus the engine will run OK. Another problem may be that the new pump is putting out too high a fuel pressure. This will result in exactly the same scenario that I described above. Put a fuel pressure gauge on the line where it enters the carb. Should be 5-7 psi.
Did the replacement pump have all three fuel line connections? There is the large rubber hose from the tank that goes to the inlet, the metal outlet line to the carb, and the smaller rubber fuel return line back to the tank. Some replacement pumps only have two lines and eliminating the return will cause a problem. Even if the new pump has all three connections, if the return line is plugged for some reason you could see higher than desired pressure at the carb.
Finally, replacing the pump on a 307 required disconnecting and removing a number of components. Be sure everything got hooked back up correctly.
btw does anyone have a diagram of the vacuum lines on the 307 ? when i bought the car there was some that was off and just laying there and one or two was pluged , i didnt think much about it at the time because the car ran fine but i know i need them hooked back up .
Take pictures, I can probably direct you. I have them memorized still and I also have the 85 Olds FSM that covers it too.
I have seen paid mechanics screw up these vacuum lines too. Once you fully understand them, they are really easy and make sense, and you will be able to look at a 307 and connect them up easily.
That mystery black box on the drivers side valve cover is nothing more than a computer controlled vacuum switch. It lets the ECM turn things on and off like EGR, EFE and rear vacuum break as needed. The top switch is EGR, the bottom ones are EFE (rear I think) and front side is rear vacuum break. Don't mess them up! You'll get EFE all the time!