BIRCHZ71

iTrader: (4)

P0131 bank 1 02 sensor
P0171(TWICE) Left bank lean
p0300(TWICE) Random misfire

truck idles horribly. From these codes Im assuming I need to replace the front (drivers side)02 sensor. From my research im assuming p0171 causes p0131 in turn misfiring(p0300)?
Thanks,
Birch

Mrgoodwrench3

The P0131 is for O2 Sensor Bank 1 Sensor 1. Left side before cat. It may not be functioning correctly. P0171 may be related to the o2 sensor, or could be a vacuum leak at the intake. Do you have access to a scan tool? You really need to see what the long and short fuel trims are. Also check the fuel pressure regulator. Remove the small vacuum hose with the engine running. There should not be any fuel at all in the hose. With it disconnected take the end of a small screwdriver and tap on it. NO fuel should come out. Try this to start.

BIRCHZ71

iTrader: (4)

where is that vacum hose...i remember where the regulator was on my old 4.8 silvy but not on this one....i looked and cant find it. 2004 5.3

jhe2003

iTrader: (7)

No mechanical regulator on your 04, I would think you have a vacuum leak, and its causing the misfires, and its just a matter of time before p0174 flags. the o2 code might not be related to the rough idle. I have read that intake gaskets leak ALOT on these trucks but it has never happened to me before!

BIRCHZ71

iTrader: (4)

well the o2 code only comes on when it idles rough......its all or nothing with the codes. One minute its running fine and i have no codes, and the next rpms drop way down and the infamous light comes on.

Wheatley

iTrader: (12)

From the sounds of it,when the idle falls,it is due to the lean condition,which will happen.
Something is going on somewhere.

budhayes3

iTrader: (19)

It could be a couple things, basically all of which has been mentioned...could actually be lean, causing a misfire, or the O2 sensor could be bad, causing a misfire and a lean code, or you could have a misfire that's causing incomplete combustion which will allow more oxygen into the exhaust stream, which will give you a lean code. Dirty MAF sensors have been known to cause lean codes also. If I were to guess, I'd say the O2 sensor is the culprit, but that's just a shotgun diagnosis...

BIRCHZ71

iTrader: (4)

Maybe i'm not inclined enough but what confuses me is the excess smell of gas when this situation is occurs. Wouldn't that mean its running rich not lean? There is no gas smell under the hood, just out the pipe. And it is strong!

Wheatley

iTrader: (12)

A lean mixture will also have a very strong smelling exhaust.
Hydrocarbons, HC's, from unburned fuel. HC's are formed from an excessive rich fuel mixture or a lean fuel mixture where there is excess air, leading to a lean misfire.

jhe2003

iTrader: (7)

its just incomplete combustion from the misfires, but the 02 sensor will only read oxygen not fuel.