Originally Posted by EllowViper
This...since your injector duty cycle references battery voltage both during crank-run-restart cycles. In layman's terms, your ECU adds or subtracts injector duty cycle based on battery voltage. You may have cranking voltage, but it saps the needed voltage to adequately power the injectors...or once running, a low voltage is telling the ECU to add injector duty cycle since the injectors will lag in their functioning. THis can result in some strange running conditions when coupled with other low voltage induced compensations. Add in the "key on" voltage settings the ECU uses to calibrate most of the 0-5v references...you can see how a weak battery can effect more than just cranking the engine.
Thanks for reinforcing the battery thing. I guess a new battery is in my future. I'll see if I can get some voltage readings on the battery before I pull the trigger on a new one.