2000 Silverado Vaccum Leak?

[Evan Dodd]

Having trouble fighting a vaccum leak or so I believe  with my 2000 Silverado 1500. Has the 5.3 in it. I have po171 and po174 lean codes and that’s it. Leads me to believe that it is caused by a vaccum leak. Already did intake manifold and have used smoke which led me to a leaking gasket on the egr, but the codes still come up once the truck completes its cycle. I just want to know if there are any other common leak points I have overlooked or what else could be causing these codes. 

[CamGTP]

Manifold gaskets, both intake and exhaust can cause the codes. The exhaust is usually because there are broken bolts on the manifolds.

 

2000's still had EGR's and those can leak at the intake causing the codes. Throttle body gaskets, the brake booster connection at the rear of the intake. Those would likely be seen with a smoke test though.

 

Then you have fuel pressure, if it's too low you can get lean codes. You should be seeing at least 52+ psi of fuel pressure and under load it should be 55-58psi.