Im back <3 with a fun one

[mAxius]

So upstream o2 sensor out car drives fine starts does what it is supposed to do.

Got new o2 sensor put in, connected it and car sputters and dies.

Idea's I am thinking it's the exhaust / catalyst had to go back to old faithful because the other 20-year-old car i have access to broke something on the right side and is thunking fw/reverse/ breaks on

[trottida]

You have a GEN3 (2000-2002)? Your precat which is part of the exhaust manifold is plugged. You'll need to remove the manifold an rip out the core of the precat to regain flow. I've heard you can do it from the bottom too without removing the manifold from the engine.

[fetchitfido]

Not sure why you replaced the O2 sensor when the O2 sensor removal test told you the exhaust was restricted.

If the exhaust is in overall decent shape (or at least weldable) and you have a welder you can drill a couple holes in it to see where the restriction is, then weld the hole up when you're done. The pre-cat is the most likely culprit, but the main converter is likely and depending on how that's failed it could plug up the muffler as well.

[trottida]

Here's what the inside looks like and what gets clogged up.

Perhaps your engine is running rich causing carbonization. Carbonization in the engine and exhaust is common in these cars when you have a failing thermostat, bad ETCS and/or fouled ETCS harness connector. For a GEN3 your temp gauge in the cluster should read around 1/3rd (see photo below). If it is around 1/4 then you likely have these issues. This would be the root cause of a clogged pre-cat. The PCM signal for coolant temperature reads cool so the engine management increases fuel to bring the engine to proper operating temperature (~193 F) which it never does because of the failed component(s). Extended running like this causes the black sooty carbon build up.

[mAxius]

Originally Posted by trottida

You have a GEN3 (2000-2002)? Your precat which is part of the exhaust manifold is plugged. You'll need to remove the manifold an rip out the core of the precat to regain flow. I've heard you can do it from the bottom too without removing the manifold from the engine.

i have one w/o the precat i think its the cat i dont think in over 295k it has ever been fully changed