I have a 1998 Navigator with 245k miles. Running like a top until last week when CEL came on with above codes. Have seen similar posts about vacuum leaks, MAF, etc as possible problems. This one has a twist. At hot idle, with scan tool connected it will cycle between CL and CL-fault. When in CL the LTFT on B2 is 2.3%, B2 O2 sensors sort of quit fluctuating. B1 LTFT is 25% and O2 sensors are normal and the idle is rough. When in CL-fault the LTFT on B1 and B2 is 25%, O2 sensors are normal and idle is smooth. The cycling between CL and CL-fault is a steady 4 secs in CL and 15 seconds in CL-fault. The MAF voltage is around .6v in either mode. The TPS doesn't change. Increasing the RPM causes the LTFT on B2 to go from 2.3% up to around 25%, same as B1 and the O2 sensors read correctly. When RPM decreases back to normal the cycling resumes. After 5 or so minutes it will stay in CL-fault and readings are good but any increase in RPM and the cycling starts again. The truck runs good with no apparent power loss. It seems like the cycling and the LTFT differences should be a clue to something and I'm hoping that one of you guys may have the answer for me. THanks

 

Sounds like the PCV elbow broke at the center rear of the intake manifold.

 

I had that problem a couple of years ago and repaired it and I did recheck it having had the problem and noting how many others found that as an issue. It must be something else.

 

Those two code come up when the engine is running very lean. That's either the result of a large vacuum leak or a failing fuel pump.

 

Is there a convention place to check the fuel pump pressure? This is a 5.4.

 

On the front end of the fuel rail, passenger side, there is a shrader valve to connect a fuel pressure gauge to.

 

I had the same problem with my '98 Expedition EB. Found out that the PCV joint going into the back of the engine was almost completely broken. I purchased another part from AutoZone, and installed it myself. It was a pain in the a** getting back there (no pun intended), but I eventually got it on. I also put electrical tape on the other jointed pcv hoses (three in all) because they had a little abrasion on the joint areas. I also cleaned the MAF sensor and my K&N filter and now she runs like a champ!!!!