2000 SLE P0135, P0420, P0300, P0336, P0463, P1811

[Orbitz]

Hi again all. I have a few questions. A couple of months ago, the car started running weird. I know there is a rattle in the exhaust, and that it scrapes on speed bumps and things that are really high off the ground (I haven't found the time to get it looked at). A month ago, code P0420 came up, and the car was having a weird stuttering issue on start up. I bought a bottle of that AC/Delco fuel injector system treatment plus, and the weird stuttering on start up disappeared. At that time, I had cleared all codes.

Today, the car had been sitting in the driveway for literally 5 minutes, I went out, fired it up, and it barley ran. It stuttered, and missed, and then quit after around 25 seconds. It took a few times to restart it, but eventually it did. It was running great, then maybe 1 KM down the road, I was making a very slight turn, and it quit on me again. It took around 5 minutes before it would fire up again, and it's back to running fine.

The MIL current codes are P0135 (02 heater circuit, bank 1 sensor 1), and P0420 (Catylist system efficiency below threshold (bank 1)).
The computer is also storing (as Fail Since Clear on my scanner) the following codes: P0300, P0336, P0463, and P1811.

Regarding the P0336, I had the crankshaft position sensor replaced a year or so ago, but never had the dealer "reprogram" it.
I also know the fuel gauge doesn't read correctly, which I assume is the reason for the P0463, but do the other codes make sense?

From what I found on here, as well as Bonneville Club members recommendations, I believe the catalytic converter is on it's way out, but could that cause all of these problems?

Sorry for the blathering. Thanks all

[nos4blood70]

Bad cat for sure. I'd start with that. You can try and unbolt the catback at the down pipe and see if the car runs better. It'll be super loud, but you will know.

[Orbitz]

The problem is, I can't seem to make the car act bad. One minute, it's running perfect, the next it's stalling out on me. Very strange. Thank you for the advise, I have ordered a converter, and will have that replaced and see what happens.

Do you think all of these codes could be connected to each other, or do I have more then one problem?

Thanks again

[SMok3-11]

P1811 is the pressure control solenoid, which can cause trans to act up if I'm not mistaking.