Hello so on my 2000 5.4 V8 F150 i was replacing right valve cover because of broken pcv baffle inside of it so i replaced it whit new valve cover gasket to, to do this job i had to remove right arch liner A/C dryer and that bracket on firewall that holds some wiring harness so i coud reach all the bolts on valve cover after installing new valve cover i torqued every bolt to 12Nm and rechecked every bolt just to be sure.
Just after this job i coud immediately notice that idle rpm is a bit higher running at 820-900 once warm and once truck is warm and i restart it starts to run rought however it will run quite alright when starting it cold in the morning so i hooked up truck onto obd scanner it poped up two codes p0153 and and p1151 see first picture, so i didnt even bother investigating so i just replaced bank 2 sensor 1 because both codes are related to this sensor, i deleted dtc and that symptoms were still there so i checked engine codes but this time i've got different code p1158 which is different sensor see the second picture, so after investigating a little deeper whit scanner all voltages off all 4 o2 sensor once truck is warm did fluctuate between 0.1-0.8V also the heater on all 4 was turning on and off also graph seemed fine so does that mean o2 sensors must be good also wiring to them? however my concern is why both sensor are stuck on lean and not switching beetwen rich/lean? see other pictures including fuel trims.
Any ideas? Why woud this symptoms begin right after replacing right valve cover coud it be just a coincidence but i've read that that happend to some others to but didnt really see the answer?

 

You have a vacuum leak or unmetered air entering the engine after the MAF.

 

coud a vacuum leak enter from a poorly installed valve cover gasket? Or whre do you think i shoud look for vacuum leak?

 

Look at the EVAP hoses and PCV tubes closely
One has collapsed or has been knocked off
Re read post two over and over until you find the unmetered air leak
Check the fuel trims to be sure

 

More likely than not, you either moved or broke a vacuum line accidentally while wrestling with the valve cover.

 

Coud be very possible that yea i was strugling quite a bit to get valve cover out and one of vacuum hoses broke i will inspect them, but pcv valve is attached to the valve cover itself so theoretically air coud find way into combustion chamber through leaking valve cover gasket but im not certain if this is actualy practically possible.

 

Your clues don't fit together well. It runs well when cold and the scanner reports a rich code. That doesn't suggest a vacuum leak. But the O2 sensor data says lean (not sure how the scanner determines that).

You only showed long term trims. You need to show both and add them together to know. And engine temperature is important

But, maybe, if the vacuum hose to the fuel pressure regulator got knocked off or broken you could have both rich and lean depending on operating conditions. I'd start there.

 

good idea i will look into fuel preassure regulator vacuum hose, thats what im asking myself to why woud it detect rear sensor as rich maybe if cat woud be clogged? Or if rear sensor is faulty or it was just some false alarm

 

Update so i did find two small vacuum leaks i will fix and it i will see if the problem goes away.

 

Yes sir, that'll do it

 

So i've just replaced those two vacuum hoses but my o2 sensors are still stuck on lean any suggestions?

i was just thinking theres no possible way that rocker arm fell off while removing valve cover and thats that causing my symptoms or am i just overthinking?

 

Reset the KAM by disconnecting the battery negative cable for a little while (5-10 minutes is sufficient).That will force the PCM to use baseline values and allow it to make needed corrections as it sees fit.

 

This is the first mention of a displaced rocker arm. What's up? Was it running rough before the valve cover was removed and replaced? What did you do to correct the rocker arm problem?

 

no it wasnt running rough before the valve cover replacment, that was just though that rocker arm coud fall out but i guess that then o2 sensor woud read rich if valve woud be closed as it woudnt get air in chamber or exhaust woudnt open?

 

I can't understand what you wrote except that it wasn't running rough before the valve cover replacement.

A 2V with a valve that wasn't opening would have a dead cylinder. Sometimes it's hard to tell if a V8 is only running on seven. Maybe the rough idle is from bringing that dead cylinder back to life.

Anyway, the displaced rocker arm complicates the picture. Good luck.