weird issue with the car. Info? suggestions?

[Wyldhorse0705]

here's the deal. 02 4cyl. Check engine light was on (catalyst something or other) So i figure converter is bad. The day i go to get a new one i stop into advance auto and have them scan the codes. guy says it might just be the upstream O2 sensor. So i get one and put it in, clear the code and go on about my business. A couple days later it's idling a little low and vibrating a little. then it fixes itself and goes back to regular idle. About 100mi after i clear the code it comes back on (thought it ran through the drive cycle and i was home free) So i go have them scan it again to make sure nothing new is comming up. Same thing. So he says the converter might be clogged, and suggests adding Sea Foam to the tank to lean out the gas a little, and clean up the injectors a little as well, and tap the converter a little to try to break up whatever is clogging it. So I do that yesterday and start it, and tap the converter some and let it run a bit. Then i shut it off, and restart it. This time when it restarts it just dies. Does that 2 more times after. (only time i've had this happen was in the mustang when then IAC went bad.) So i start it again and before it dies i give it a little gas to keep the RPMs up. I let off the gas and it idles WAY low and surging. It doesn't shut off but the surge is from about where the car would cut off, and 100-150rpms. I let it go on for a bit trying to think of what it could be, but then it just idles itself back up to normal and no problems.

Any ideas on what this could be? I'll post the exact codes when I get back from lunch. I have them in the car.

[Wyldhorse0705]

16 views and no replies??

Ok the 2 codes that came up are the same, but 1 is pending.

P0420
Catalyst Efficiency Below Threshhold (Bank 1)

[Mole]

Catalyst System Efficiency
Below Threshold
(Only for California Spec.)

 Three–way catalytic converter
 Open or short in heated oxygen sensor (bank 1, sensor 2)
circuit
 Heated oxygen sensor (bank 1, sensor 2)
 Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
 A/F sensor (bank 1, 2 sensor 1)

looks like you need to replace your O2 sensor/cat... trace to see if anything is disconnected first.

[Wyldhorse0705]

well i've replaced the upstream o2 sensor, guess that only leaves 1 more, then the cat haha. I'll probably just do the cat. $150 installed is a hell of a price. Thanks for the info