Engine Code's P0171 & P0174 ?

[Yukon&Tahoe]

The following is in regards to a 2000 Chevrolet Tahoe LS 4X4 w/ 5.3 V8 Engine (K&N Filter) @ 173,000 miles .

The Tahoe has speratically been throwing codes P0171 & P0174 (Bank 1 & 2 Lean) when the air temperature is 5°F or below. I have a K&N filter, so I guessed oil on MAF Sensor, I cleaning the MAF with electronic parts cleaner and reassembled. It did look cleaner when I was done!! No codes for a couple days and then the temp dropped to 2°F and code came back. No coolant being used or engine overheating so ruling out the thought of head and intake gaskets (tried the carb cleaner along gasket trick, and nothing). Could it be O2 Sensors? Find it hard to believe it would be both. It seems to run and drive fine.... with or without codes!!

Note: It did this to me last winter also and absolutely no issues (codes) over the spring-summer-fall months.... I only have a code reader not scan tool, so no other specs available.

Another Note: I did replace the Fuel Pressure Regulator this fall when it failed.... hard starting, gas in vacume line when pulled of regulator.

Any ideas???

Thanks

 

[JennaBear]

Really dirty or bad MAF.

 

[Yukon&Tahoe]

Souldn't be dirty, as I've cleaned it about 3-4 times in the last 2 years!? I thought about a failing MAF Sensor, but thought it would do it more oftern than just in that temperature range (5°F and below).

I generally notice it at that temperature range, and it usually comes on just after hitting the freeway (70 mph) after the on ramp..... which is about half mile out of work parking lot, with no stop signs.

Maybe I'll just chaulk it up to a "Mystery of Science".... until something craps out (fails) all together!!

 

[JennaBear]

I would put my money on a bad MAF, fuel filter or pump.

Sent from an ice cream sammich.

 

[Yukon&Tahoe]

Filter was replace last spring..... maybe 6000 miles ago. Pump, could be, it was getting loud just before filter change. But it's quiet now (only normal GM pump whine, would be better stated).

Just wait and see..... and hopefully I won't be "waiting" at the road side (if it's the pump)!!