Hi,
The negative trims indicate the computer is trying to lean the fuel mixture. Have you checked fuel pressure to make sure it isn't too high? Also, are there any strange odors coming from the exhaust or rattling sounds? The catalytic converter may be plugging.
Do me a favor. Take a look through this link and let me know if it mirrors what you are experiencing:
https://www.2carpros.com/articles/bad-catalytic-converter-symptoms
If it does, take a rubber mallet and tap around the catalytic converter to see if anything sounds loose inside it.
Additionally, checking for diagnostic trouble codes can be extremely helpful. You mentioned the fuel trims, but are there any codes present?
Also, if you haven't check fuel pressure, I recommend it. Here is a link that explains in general how it is done. Additionally, the attachments below are specific to this vehicle for fuel system diagnosis. Pressure may be too high due to a faulty regulator.
If you are questioning the catalytic converter, remove the upstream oxygen sensor to see if it changes how it runs. That will allow additional air to escape. Or, here is a link that shows how to check a catalytic converter:
https://www.2carpros.com/articles/how-to-test-a-catalytic-converter
Let me know what you find or if you have other questions.
Take care,
Joe
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Saturday, May 1st, 2021 AT 8:21 PM