Truck is a 2000 silverado 4wd 5.3 and i have got this awful set of lean codes (Bank 1 and 2 system lean) The truck has a rough idle and started after i changed my knock sensors i.e intake gaskets are good, 02 sensors are good, and i ran some seafoam through the gas so its not the injectors either. This problem is getting expensive, could it be the pcv valve/tubing? the little sensor on top of the intake manifold under the engine cover,with the black plastic tubing and green service cap? or where the egr tube goes into the side of the intake? Please help i need to find the fix asap!!

 

How do you know the intake gaskets are good?

 

They are brand new and I torqued them down to spec and used the tightening pattern. They shoud be sealed fine

 

Just checking.

You would need to find the vacuum leak allowing the air in.

Have you tried un plugging the MAF to see if runs any better? it will set a light for the MAF but see if it also sets lean codes.

Also look into the FPR Fuel Pressure Regulator and Fuel Pressure. These 2 things can cause hard starts and lean codes as well.

 

Sounds like a bad fuel pump. Put pressure gauge on the test port.

 

The fpr was changed about 3 months ago, and this problem started happening right after changing the knock sensors so it leads me to think of the pcv, or any other small systems part like that. I'll check out the fuel pressure though just in case. Fuel pump is about a year and a half old. Maybe it could be the maf I will also give that a shot

 

I changed the fuel filter today an reset the codes and they came back. The filter was pretty bad but I guess it wasn't the problem

 

Did you test the actual pressure though?

 

I'm going to do that this evening. Any other suggestions as to what it might be?

 

Intake gasket fell out of place while you were installing the intake and you have a vacuum leak.

Find someone with a smoke tester and get the intake smoke tested.