I'm getting the exact two codes. I'm going to try cleaning the MAF first. Not sure if that's the culprit.

 

Did you clean the MAF, and did it work? My CEL is still on and I haven't done anything yet, but my idle seems to be getting worse, so I guess it's time to do something.

 

You're not doing your vehicle, waller or our environment any favors by looking at a CEL for a few months. The situation will not improve with time, and the CEL won't go away on its own until the bulb burns out.

Start by finding out what the codes are telling you. Actron.com, among other web sites, has code meanings. If you've not read codes in the past two months, have them read again to make sure that nothing newer has surfaced as damage continued. That will get you moving in the right direction. Once you know what the codes say, the next decision is whether you pay a technician to properly diagnose the ultimate problem--or replace a few parts and hope your parts cost is less than a tech would charge.

I've used both approaches--sometimes i win, sometimes not--but i always learn something in the process. Good luck.

 

I did talk to the indy shop I use and he said the codes were indicating the problem was the MAF and that it probably needed to be changed, but sometimes cleaning does the trick. He also said it's not a problem until it starts to degrade the performance, which I would notice via a rough idle, which just started occuring, and is the reason I am revisiting this now.

 

Good deal. There's some good info here on cleaning the MAF. Used CRC's aerosol when i did mine--but i had very little oiling anyway. That's a good thing.

 

Getting the same codes, and reg is due is a couple months.
Recently cleaned the MAF sensor, so that shouldn't be it.

I replaced the upstream sensor, but now at 207K miles, have never replaced the Downstream one. I cleared the errors and now after several days and more than 100 miles, it hasn't come back but I've cleared it in the past and it comes back.

I'm on my 2nd aftermarket Cat from Magnaflow (1st one just went to pieces).

So....all this being said, how do I determine if the problem is with the MAF, the
02 Sensor(s), or the Cat. Replacing all of them would exceed $1k and I'd like to narrow down the problem.

 

Unfortunately I don't think there's an easy way of troubleshooting this without emission testing equipment. Logging live data at various speeds and checking the MAF readings is possible, but I think actually testing the pre- and post-cat O2 sensors and cat efficiency properly requires emission testing equipment.