Q: When I press the gas pedal the vehicle misfires

The code P1128 means that the heated oxygen is swapped from the circuitry. Check the wiring on the O2 sensor and check the condition of the O2 sensor. If the sensor is working fine or you have replaced the sensor and the code still comes on, then there could be a problem with the mass air flow (MAF) sensor or a vacuum leak.

First, look for any vacuum leaks. Check all of the hoses that are connected to the intake manifold and see if there are any vacuum leaks. If there is a vacuum leak, then fix the leak and check if the code comes on. If there is no vacuum leak, then check the MAF sensor for any corrosion or debris. Remove the MAF sensor and clean it. Once it is cleaned, put the MAF sensor back on and retest. If the code comes back, then the MAF sensor is malfunctioning. If you need further assistance with your engine, then seek out a professional, such as one from YourMechanic, that can help you with the gas pedal issue.