wmburns
SN Certified Technician
IMO, it's possible that both codes are related. Suggest focus on the P0203 DTC as this could easily cause the P0303 DTC.
The P0203 could be a bad fuel injector, bad/loose connector, wiring harness fault, or bad PCM injector driver.
To rule in/out a bad fuel injector, either swap with another cylinder or use an injector cleaning/flow test service such as injectorrx.com.
Once the injectors are confirmed good, inspect all connectors. Look for bent/pushed pins. Check that the connectors are fully inserted.
The next step involves testing the resistance of the wiring harness between the injector connector and the PCM connector. It will be necessary to remove the PCM for this step. If there is a problem in the wiring harness, it will have to be tracked down and resolved.
Since this is a recent motor swap, the possibility of wiring harness damage should be considered.
If the wiring harness is OK, then it is likely that the PCM is bad.
IMO, the bogging at low RPM is a combination of the PI swap and the misfire. If this were my car, I would not pay any attention to the bogging symptom until the motor runs DTC free.
The P0203 could be a bad fuel injector, bad/loose connector, wiring harness fault, or bad PCM injector driver.
To rule in/out a bad fuel injector, either swap with another cylinder or use an injector cleaning/flow test service such as injectorrx.com.
Once the injectors are confirmed good, inspect all connectors. Look for bent/pushed pins. Check that the connectors are fully inserted.
The next step involves testing the resistance of the wiring harness between the injector connector and the PCM connector. It will be necessary to remove the PCM for this step. If there is a problem in the wiring harness, it will have to be tracked down and resolved.
Since this is a recent motor swap, the possibility of wiring harness damage should be considered.
If the wiring harness is OK, then it is likely that the PCM is bad.
IMO, the bogging at low RPM is a combination of the PI swap and the misfire. If this were my car, I would not pay any attention to the bogging symptom until the motor runs DTC free.