I have a 1997 F150 I just recently purchased. When I first got it, it was indicating a cylinder 1 misfire, so after inspecting things and checking for the obvious: (spark plugs, vacuum leaks, fuel injector) I decided to reset the computer and let it pick codes back up. Tonight I decided to take it for a trip down the road and the CEL didn't illuminate right away, but it started acting very strange. When I stopped the rpms would hit 500 then kinda die every time I stopped. Did it like several times. So I scanned to see if any codes popped up and the only one was P1151. I didn't check the plug that connects to the bank 2 sensor because it looked fine, but I did check resistance on the sensor and it checked out ok, so I doubt the sensor itself is at fault. This truck does still have all original cats. I typically have them all removed because they usually are nothing but trouble, however I just got the truck, so I haven't had the chance. It wasn't doing this the other day.

 

Following this thread as I’m also throwing this code with similar sporadic bog downs. For what it’s worth, I have a known intake manifold leak that I plan on fixing this weekend by replacing the manifold & gaskets (plus a bunch of other stuff).

 

Possible causes are:
Faulty Upstream Oxygen Sensor Bank 2
Fuel pressure high or low
MAF sensor dirty/defective
Vacuum leak on engine
Leaking fuel injector or fuel pressure regulator Faulty
Powertrain Control Module (PCM)

Read more: https://www.autocodes.com/p1151_1997_ford_f150.html

So quick easy things to do are check maf sensor, Check for vacuum leak (rubber lines can be a source of the leak), throw on a gauge and Check fuel pressure, and you said you confirmed the sensor is good, if not confirm it's working, and I believe you can pull the hose off the FPR to check to see if it's working properly.

 

Update... so I reset my computer again ran to the auto parts store to see what some upper induction seafoam would do. Take note that previously it was throwing a P1151 code and that was all. After resetting it and using the seafoam in efforts to clean the engine, I took it for a test run it continued to die at stops every time. Then the CEL illuminates a misfire. Previously it was doing this saying cylinder 1 was misfiring, now it says cylinder 4!? Only thing showing up at this time. I've literally checked everything and all the basics. I'm starting to wonder if the cats are stopped up. It still has 4 of them, I'm assuming the original. If nothing changes there, I'm figuring the engine is pretty much gone. Has a super heavy fuel odor from the exhaust.

 

So another update... earlier I went outside to fool with the truck again, and I definitely found an issue. I noticed my fuel injectors were constantly shiny as if they were wet. I knew there was no way, especially after me driving it and it getting warm. So above the injectors on the fuel rail, the bleeder valve is leaking, and it's quite noticeable. You can see it coming out of the top of the bleeder streaming down the side and gradually dripping down to the injectors. This must be why my truck's CEL was triggered with a P1151 code. I've also had a cylinder 1 misfire code and a cylinder 4 misfire code. Ironically the misfiring cylinders are all on the same side as the leak. I'm going to just replace the valve and see if it works the magic. Btw... if any of you are wondering or find yourself needing a fuel pressure relief valve in the future, the part number is CM3461. I've done research online, and apparently this part is like the same valve on all later Ford vehicles. It's somewhat universal to most Fords. Going to see if this works. Thanks!

 

Jtfarra, did you ever get your CELs to go away? Or have you tried anything else (short of removing the CEL bulb from the cluster) to make them go away? I noticed that you & I are having a lot of the same issues & codes. You recently replaced the intake manifold gaskets, I also replaced the intake manifold & gaskets too.
Anyways, after replacing my truck ran great for a short time & then it started giving me rich codes (P0172, P1132, P1152) & a cylinder misfire code (P0301 & later a P0308). So as of now I’ve order new oxygen sensors. I have a hunch that this may be (or at least part of) my problem. I’ll report what happens after I get the O2 sensors installed. Fingers crossed.