sooooo driving the BII like I always do....except now she started to miss badly and was way down on power.... ut oh.
Made it to our gate and parked it, got a ride to town. Came back later, started her up and CEL!!
Limp home, still down on power, plug in scanned check codes.
Manufacture specific codes, P1131
Read pending codes, shows 02 sensors upstream bank 1 lack of switching, reading lean.
I inspected the wiring to the upstream sensor bank 1 (pass side) all looks good. Getting that 02 sensor out on my Bronco would require DROPPING THE EXHAUST PIPE! Not fun. I can get a 7/8" wrench on it but not enough room to turn. No way to hit it with a torch for heat and then a 02 sensor socket without dropping the pipe.
So discouraged I moved on to more testing. Finally I hooked up the scanner and looked a little deeper into the PCM
Turns out there were some pending codes! good. Two P1131, HOS11 ( means heated 02 sensor bank 1 sensor 1) now and pending, then another 1131 this time HOS21!! Bank 2 sensor 1 is lack of switching reading lean also........okay so now I know its not an 02 sensor.
Time to go for a drive and watch live data...... Im starting to lose sleep over this! Wife and I have 4 trucks, FJ, Bronco, Excursion, and F350. Wife has been driving excursion because her FJ is waiting for all new steering parts........ I need the Bronco!!!!
So driving truck watching live data, I see the 02 sensors are definitely switching
Usually when both upstream sensors have lack of switching and read lean CODES, houston we have a problem, this means:
Low fuel pressure
Large intake leak
Large vacuum leak
Dirty MAS, leaky air intake
Full inspection of 02 sensor wires, air intake, MAS, upper plenum, all vacuum hoses, PCV system, everything checks out. Fuel pressure test shows pressure jumps to 42 psi immediately. .checked all fuses, So far I have found nothing wrong! I cleaned some connections in the fuse box
Cleaned mas, re sealed intake tube from air filter to throttle body. Cleaned throttle body. Checked all vacuum lines and hoses, inspected plenum gaskets for soot entry.... nothing! Truck looks like the day I put it together, only dirty.
Finally I found it. I had to use a mirror to see it on my BII, but the PCV valve had come up out of its grommet!! I pushed it back down with a blunt screwdriver....put it all back together and time for test drive.
Two day fiasco put to rest.... back on the road with my 1997.5 02 sensors lol
Drivetrain has about 105K miles on it now, the BII is still just a baby.
So 5.0 dudes let this be a lesson to us
In this case the P1131 code was PCV valve popped loose
I am SURE it will happen again, once they come out of the grommet they keep coming out of the grommet. I will have to do some fancy stuff to gain access to the area, but eventually I will replace grommet and PCV and add some silicoln to keep it seated.
I then spent about 3 hours spring cleaning the Bronco
SHES A GOOD GIRL!!!!!!!