The car will only run if I remove the top O2 sensor?

Hi,

It sounds like you have a plugged catalytic converter. When you remove the top (upstream sensor), you are allowing exhaust to have a place to escape before the converter. When it is reinstalled, there is no place for exhaust to go.

Here is a link that explains how to test a catalytic converter. There are different approaches to testing, so the one where it suggests checking how the vacuum react with it running will require the sensor to be removed.

The catalytic converter is integral to the exhaust manifold, so I want to be sure that is the issue, but at this point and based on your description, I feel that is the issue.

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