Hey guys and girls,

Well after doing another shakedown drive from the maintenance job I recently completed, I got a check engine light that shows the infamous P0171 and P0174 system lean in bank 1 and 2. I've read the discussions on here about what it could possibly be, but havent seen a definitive follow up on the fixes.

From what I was able to read, it’s either a vacuum leak or fuel pump or MAF sensor/O2 sensor.

I think I’m going to rule out MAF and O2 since I never touched them during the maintenance. I would be surprised if I all of a sudden had a fuel pump failure. So I’m leaning towards vacuum leak.

Has anyone actually solve these check engine light issues?

2013 V8V ~17k miles and recently did engine oil/ gear oil/ brake and clutch fluid replacement and spark plugs and throttle body cleaning. Thanks

Andrew

 

Vacuum lines to the secondary air injection valves should be checked. If you check the RH side by the EGR there is a double plastic line that goes to the single source with a 1 way check valve. Since heat plays a factor to longevity, the hard plastic lines can be brittle.

 

Interesting, I will check that. Is that the two to one you are referring near the EVR Outlet Hose?

I took measurements at idle.
Short Fuel Trim is around 10 and Long Fuel Trim is around 20. Under load, it drops to single digits. (This led me to believe it was a vacuum leak)
MAF sensor reading at idle is around 7-8g/s (seems normal). That's why I ruled out faulty MAF Sensors
Fuel Pressure Valve at idle is around 380kPa ~ 58 psi ~4bar. (seems normal) That's why I ruled out fuel filter/pump/injectors.

Now interestingly, I heard a very faint buzz coming from my PCV valve and when I pushed on it, it changed tunes. It was very faint, which is why I missed it the first time.
I went to Jag/Land Rover and bought a new part. installed and the buzzing was louder than my engine. They sold me a defective part.

From my understanding, if the PCV buzzes, the valve is stuck open. Since the valve is open, it lets more air through and causes it to run lean hence the code.
I did a cheap smoke test (cigar smoke haha) and blew it through the intake duck and did not see any signs of smoke leaking out.

Thoughts? Thanks for posting your idea and helping.