Usually after filling her up she acts up. In the morning I start it n it idles low as if it wants to turn off. I need to keep my foot on the gas to stop her from turning off. After a minute or two wen it's kinda warned up, ill drive but the idle is still low. Usually to make it go bak to normal I give it gas. Go to about 7k RPM n it back fires. After 2 or 3 loud pops she runs normal. As if she has a sore throat or sumthin n I need to get it out of her system. It's a 89 iroc wit flow masters so this process tends to wake people up. I have a 350 under the hood. So my question is why does this happen? Fuel pump? Spark Plugs? Distributor?

 

Is this a backfire, as in firing back through the throttle? Or is it report from the exhaust. These are two completely different things and have different causes. I'll bet that it's exhaust report and say that most likely, combined with the poor idle on start up, it's a fueling issue. The exhaust report would be excess, unburned fuel getting into the exhaust. Injector issues are common on stock TPI motors of that age. It could also be an ignition issue but I wouldn't expect that to clear up by revving the engine. Is your engine stock? If so, I wouldn't recommend revving it past redline too often.

 

I'm thinking reports too, and while I'm pretty new to these cars I'd say you may be getting raw fuel through your evap system since you say it's after a fillup. I had this happen to me one time after topping off a tank as far as I absolutely could (for no good reason). Problem went away after a few miles.

 

That does make sense. I missed the connection to filling the tank. A saturated canister could cause symptoms like this.