P0171. Again?

[TonyKarter]

P0171: Fuel Trim System, lean bank 1

Started the car up in the Academy parking lot and immediately got this code. Went to OReilly's and got it read and cleared. Put thirty miles on it and it has not thrown a code again. It threw this code about this time last year, and when I cleared it then it did not come back until yesterday.

Anybody have an idea why this happened? Also, what confuses me is why only lean on one side? I've had to jet some of my boat motors fatter on the top two cylinders. For whatever reason top cylinders usually run leaner than the four cylinders below, but lean on only one side in our fuel supply configuration? How can one bank be lean without the other bank also being lean? That puzzles me. Any ideas?

[AuuuSSSIII YA' LATA]

Check for any type of vacuum leaks. Recently done any work to the top end of the engine?

Straight from GM: Some customers may complain of a SES light with no engine performance concerns. Upon inspection DTCs P0171 and/or P0174 will be found with a Tech 2. This may be the result of unmetered air entering the PCV system by way of a valve rocker arm cover gasket or filler neck/tube leak.

GM also has a bulletin that explains this code may be set due to slightly clogged fuel injectors, not to say you should go replacing them but it could be the fuel you put in the car.
Dunno if they switch to winter fuels in TX, but if you were getting the same code around this time last year and once cleared takes a little to set again. Just a few suggestions. Good luck

[AuuuSSSIII YA' LATA]

Check for any type of vacuum leaks. Recently done any work to the top end of the engine?

Straight from GM: Some customers may complain of a SES light with no engine performance concerns. Upon inspection DTCs P0171 and/or P0174 will be found with a Tech 2. This may be the result of unmetered air entering the PCV system by way of a valve rocker arm cover gasket or filler neck/tube leak.

GM also has a bulletin that explains this code may be set due to slightly clogged fuel injectors, not to say you should go replacing them but it could be the fuel you put in the car.
Dunno if they switch to winter fuels in TX, but if you were getting the same code around this time last year and once cleared takes a little to set again. Just a few suggestions. Good luck

[gr8lover]

If its only one side..... probably just the 02 sensor flacking out.....

[TonyKarter]

Thanks guys. The O2 sensor went through my mind, thinking it might be bad on that side. The prescribed fix (according to OReilly's computer) is replace the fuel pump/module. Low line pressure...lean out. Wish I could get some data on the exhaust gas temps on all 8 to see if any cylinders are running lean. I need a better infrared gauge.

[shane]

If its only one side..... probably just the 02 sensor flacking out.....

i agree.