2010 Challenger rt, 100% stock.
Rough idle/missfires only on cold start ups, even if 90°F outside. Runs and drives 100% fine after up to temp, wide open throttle not affected.
Recent services:
Spark plugs replaced 4k miles ago (ngk LZFR5C11 coppers)
All 4 o2 sensors replaced with very cheap off brand sensors 2k miles ago.
This issue began 2k miles ago just after cheap o2 sensors.
Question: Im sure the cheap o2 sensors caused this, but can anyone explain why? Do these sensors read just slightly different than oem sensors, causing the computer to inject more or less fuel resulting in spark plug issues/missfires?
More info: There are some strange things going on with spark plugs, I made a descriptive video on youtube, click this link:
https://youtu.be/CSzS3DF9n14

 

On cold startup, the PCM ignores the O2 sensor for the first couple minutes of run time. Takes time for them to heat up, and actually start working......

As for 'cheap' O2 sensors, how is your gas mileage? Any better/worse than before? Engine run good otherwise?

As an experiment, you could unplug the front O2 sensors, and see if the problem goes away.