Lean condition codes P0171 P0174 how to troubleshoot

[sctrl]

Hi all,
Got lean codes recently, several times. No other codes. I did notice real-time random misfires on various cylinders, no codes though.
I’m guessing it might be vacuum leak. But I also noticed low fuel pressure on the freeze frame. Can you guys check attached freeze frame data to confirm my suspicion.

 

[Fless]

Fuel pressure: 297 kpa is a bit over 43 psi, which is a pretty normal value for these engines when running.

Both banks are lean and there's a lot of fuel being added (long term, anyway) so I'd be looking for a vacuum leak after the MAF and around the intake, for starters. I'd also clean the MAF or substitute a known good MAF.

Might also do a standard vacuum test with a gauge on the manifold.

Graph the upstream O2 sensors to be sure they're active (I see it's in closed loop, so that's good).

One other SWAG is to verify that the purge valve (on the engine) is fully closing. It's commanded at 80% but when it's supposed to be fully closed, is it?

I'm sure others will have suggestions.

 

[swathdiver]

Hi all,
Got lean codes recently, several times. No other codes. I did notice real-time random misfires on various cylinders, no codes though.
I’m guessing it might be vacuum leak. But I also noticed low fuel pressure on the freeze frame. Can you guys check attached freeze frame data to confirm my suspicion.

I have leaky intake gaskets and my LTFTs are in the negative, not positive. Are any of the cylinders misfiring? I would pull the plugs and examine them.

Now, did you just refuel? Trims are all over the place while the vehicle calculates the new alcohol content for a while after refueling.

Have you sprayed some water between the cylinder and intake manifold on both sides while watching the O2 sensors? (test for leaky intake gaskets)