Chevy pickup problem

[IMCA38]

Any Chevy techs here that can help me out?
I have a 2005 K1500 with 5.3L V8. (code T if that matters)
A while back, I had the check engine light coming on under hard acceleration.
I scanned for codes and got a code for MAF problem (101 I think). I checked for air leaks, cleaned the MAF and cleaned the K/N filter. Still had the light, so I replaced the MAF. That took care of the light coming on under acceleration.
However- A few days later, the light came on again while sitting at a red light idling. Re-scanned and now shows code 171 and 174 for lean on left and right. After reading some Chevy forums, it sounded like an intake gasket leak might be the problem. I did the carb cleaner test up and down the intake and didn't find anything.
Given this information, are the upstream oxygen sensors the likely culprit now?

Thanks!

Todd

[WilliamBos]

What does the exhaust look like?? Smoking black? Is the mileage terrible??

Lost sensor 1, Bank 1 (front oxygen sensor, drivers side.) and it took the Cat out with it. Got a new Y-Pipe covered by Federal Emissions warranty, via GM.

Maybe get it to a dealer, and have the diagnostic done, just state you want a print out, and no repair done. That Y pipe was $1K.

Mine is an 04, same VIN code 5.3L.

[IMCA38]

I haven't noticed any black exhaust. Mileage may be down a little, but not much (1 MPG +/-) . Seems to run OK also.

[WilliamBos]

ok. When I lost sensor1, it was dumping raw gas into the cat, smoking like an old diesel, and burnt the cat out.

A tank of gas did not last too long.

[Dmace]

O2 sensors rarely go at the same time like that and if they did, you would see a code for at least one.

Since both sensors are reading a lean condition then the problem is something that affects the engine on both banks. I think it's still a MAF sensor or intake leak. I've received bad MAF and other electrical parts from stores before.

If you have the old MAF, plug it in and see if you get the same symptoms as before. When is the last time you cleaned the K&N? Is it possible you over-oiled it?

[WilliamBos]

To add what Derek suggested, if you have the factory airbox and filter, put it back in, until you resolve the issue.

[Diamondpilot]

I saw this on a V8 Lincoln Aviator. Ended up being a combination of a bad PCV valve hose and a bad hose going from the break booster to the intake.

Chris

[CLinton_in_FL]

My guess is the intake gasket. I had my engine light come on every winter because of the cold. Replacing it is not that bad. Or you can just wait until the summer, and it will go off

[Stihlrunner]

You might look up Technical Service Bulletins for that. I remember seeing several on aftermarket oiled filters.

Also, throttle body butterflies can get regularly gummed up and wont close completely causing and air reading problem. Believe there to be a TSB for that also.

[CowboyRon]

I had one of those codes showing maf, and it was my fuel pump. We put a pressure gauge on the fuel line and it wasn't getting enough fuel.