The night this problem started, my car was having trouble reving past 2.5K and it was reving up very slowly. It was intermittant at first, then started getting worse. The car was running super rich. It smelled bad and I used about 2.5 gals in only 30 miles. Then it started stumbling between 1-1.5K (was subtle at first, car felt like it was rocking slightly back and forth).

Then eventually the CEL went on (code 44, O2 sensor lean).

I switched the O2 sensor, waited for it to get into closed loop, and there's no more CEL, it doesn't run rich, and it idles smoother.

However, I'm still having the problem where it doesn't want to rev over 2.5K. It revs slowly to that point, then it barely moves past 2.5K. If I hold the gas, sometimes it will make past, but usually not.

The car also sounds like a damn Honda r1cer. It's very loud, seems like from up front. But there's not as much of a nice v8 rumble from the tailpipes.

Could my O2 sensor have fouled the cat in only 3,000 miles? I got a new cat about 8 months ago. How can I test if the cat is clogged?

I've done a lot of work in the past 2 years, and recently trying to fix a similar problem: https://www.thirdgen.org/forums/tech...owly-when.html

 

disconnect the exhaust before the cat and start it and see what happens that will bypass the cat also why was the cat replaced in the first place maybe a tuning problem