Hi Payjobs,
Even though it is not counting misfires, does not mean that it is not misfiring. The way the PCM counts misfires and then turns the light on is by not seeing a crankshaft acceleration after it fires the spark plug. If it sees this acceleration then it will not count until it sees other indicators showing a misfire.
We need to determine if this is actually misfiring by looking at the o2 sensor data. See what your short term and long term fuel trims are and send me those numbers while it is running rough.
The fact that it does not start running rough until it warms up indicates that this is switching to closed loop which means it starts reacting off the o2 sensors.
This could mean you have a faulty o2 sensor or a different sensor giving the PCM bad data, or the PCM itself.
However, we need to start with if it is actually misfiring and the o2 data will tell us that. Send me those numbers and we can go from there.
Here is a bunch of resources that will help point us in a better direction. Thanks
https://youtu.be/QTE8k06MzwQ
https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor
https://www.2carpros.com/articles/engine-vibration-at-idle
May 8, 2019 at 8:05 AM
