lean fuel mix

[painthorseowner]

I have a 2006 sierra z71, 5.3 v8 engine code T. Have been having problems with error code for a lean fuel mix, in one bank. Funny part is, the light only comes on when engine idles for a bit. Then, it may stay on a day, a few days, then go off going down the road. will stay off usually as long as engine doesn't idle for long. No noticeable drivability problems. The engine was replaced with a crate motor but this had been going on a few weeks prior to engine going out. I've been told it could be the mass air flow sensor?

 

[shadyowl2]

It could be a vacuum leak somewhere in that bank. It also could be the mass air flow sensor but you would get a code for that most of the time and have a driveability problem. Which bank is it 1 or 2? Check your oxygen sensor readings on a scanner to make sure they are in spec for that bank.

 

[painthorseowner]

Bank 1, and it only comes on if the truck sits in park idling for a bit. The error code only read lean fuel bank one. I had to replace both the vent valve( sits on side of gas tank) and the purge valve because THOSE had error codes as well, but now just the lean fuel bank 1 code.....and, again, only if idling. Odd....

 

[happy 2011]

well i can tell you this. It's not the mass air flow sensor. Both banks would need to be lean for it to be the sensor. A mass air flow sensor can not make only one bank lean. Think about it

sounds like you have a small vacuum leak or a lazy o2 sensor.