guys just got out from under a truck payment on a 07 tacoma and bought an 04 xterra cash for 4900. Runs well and was taken care of but of course with 176,000 miles ill have some tinkering to do. So far the codes are sayint catalytics although it passed emissions. Also there is a slight loose or rattling sound under the hood. Other than that Im happy with it. The 377 I spent monthly on the tacoma will be spent on modding up my black on black X. Im excited.
The cats could be starting to clog on the return line where the sensor is connected to which would flip the code. In the long term that might cause back pressure that will make the engine run choppy before it really fails emissions.
But it sounds like you're going to be flying through this project! Have fun, and good luck with all the mods you're going to do!
I had the random, tinking, underhood sound you might be describing, and various, including catalyst, codes were logged on my newly-acquired '00 X. It kind of sounded like it was coming from the head. Lying underneath the car, using a stethoscope, it sounded like it was coming from the rear O2 sensor.
The tinking sound was caused by melted and re-frozen catalyst rattling around in the passenger side cat. Here's a shot looking up into it at what I found. I broke this lump out and the sound and the code went away (well, I had to clear the code, but you know what I mean).
I'm sure the catalyst will melt like this if a bad mis-fire is left untreated too long. Unburnt fuel burns in the converter.
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