Guys, something worth checking out if you're having a persistent p0171 lean code despite replacing multiple sensors + PCV kit install. I had this same issue on mine. After using the PCV fix kit v3.4, the code still showed up. What it ended up being was the junction btwn the intake manifold's PCV exit port (the one in the center pointing straight up) and the female connector that clips on. The gasket/o-ring retained within the latter very easily falls out, and the kit online only sells the retaining ring and NOT the gasket...weird. But you can buy an O-ring kit at any auto parts store and put several between the two, or go w/a gasket maker, and after re-connecting the code's gone away. The thing that gave it away was the hissing sound. The online simpler forums talk about listening for "hissing" in the valve cover's vacuum valve - which we all know actually isn't the PCV valve - but they're right that at idle your intake manifold AND crankcase will pull a vacuum. I ended up hearing this same sssss coming from the intake manifold pcv outlet/connector junction, and knew I'd found it. If this junction doesn't end up being the root of your problem, I suggest the following:
- Turn your engine on in park
- Take a tissue, or use your ears if you've got good hearing, and follow the intake line from the MAF near the air filter through the system all the way to the manifold. Wave the tissue near the joints and see if it gets "pulled" into the system anywhere to signal vacuum. Listen for the hiss.
- Also do this to the PCV lines - turbo, manifold, evap lines if you've used the replacement kit - and look for the same.
