Im having a lil trouble trying to figure out wether or not my upstream sensor is causing this issue. Maybe one you guys here could help.

Im pulling a P0171 Lean code for only one bank. The car will not pull this code during everyday driving conditions. The only way I have pulled this code is if I drive the car in an excess of 70mph. I have checked all the intake piping, hoses, etc but no leaks.

So here are my questions:
Does the secondary fuel pump kick on during this particular MPH?

If not, then its most likely a sensor?

My other alternative was to swap the sensors to different Banks to see if its replicating on opposite sides.

Whats your thoughts. Thanks

 

OMG, Exactly what has happened to me. Lean code P017x, (can't remember last digit) amber check engine light came on, but as it was still below 3000 revs restricted performance didn't actually happen, though as I remember warnings did come on.
This only occurred at 70mph. and above. (Sometimes didn't notice it until reaching 75, remembering, and taking a look.) Never did find out what caused it. However, that was on mainland UK (70 limit) but I live on a small island with a 40mph limit so hasn't re-occurred, Although I did get it to 75+ one quiet evening, on a virtually empty, long, almost straight road, had no problems, no lights, no warnings, and ran great.
When I got these occurrences in UK, I used the OBD11 code reader (Thanks Sean- good advice) to get the codes and delete them. The engine light and restricted warnings came back at 70 mph each time for some days, then seemed to stop. (I deleted codes using OBD each time it happened.) Perhaps I just didn't drive over 70 for a while, can't remember!!

 

It appears to be closer to the 75mph range as you stated. I can delete codes all day long but this is damaging my fuel mileage and eventually the car itself so I would like to nip it. We all know how pricy some of these parts can be to be replacing parts as trial and error.

Quite honestly Im surprised no one has an answer to at least the secondary fuel pump question. Its has to be a fuel issue as if it was a vacuum leak the car would do it all the time. Is there a fuel pressure rating the car is suppose to be at?

Any help would be appreciated

 

The secondary fuel pump kicks in at a engine speed, which I believe is 3000 rpm. There is no fuel pressure sensor. The best way to Troubleshoot fuel delivery is to get a test gauge and tape it to the outside of the windscreen (so a leak does not blow your a** up!) The pressure should hold at a little over 40 psi above manifold pressure. You might have a fuel filter problem or even a MAF issue. Have you cleaned the MAF element?
Trending the LTFT and STFT can be useful for your diagnosis.
You did not say, but I assume we are working on an XJR, right?