I have 2002 Ranger XLT with a 4.0L and I replaced that POS PCV elbow at the intake manifold, got rid of the PO171 and PO174 codes but now the engine won't idle and stalls in gear if you take your foot off the gas. Prior to finding the cracked elbow I changed the mass air flow sensor and the fuel filter, cleaned the IAC, checked and cleaned the PCV valve. The engine purrs like a kitten with the busted elbow installed, dies whenever I put the new elbow on. The codes usually come back in two days or so with the old elbow on and I can't drive it that long with the new elbow so I don't know if they will come on with that one or not. Fuel pressure was running a little high at 75 lbs. but I don't know if that matters. Any help would be greatly appreciated this has me and my mechanic stumped...

 

Tried tapping on the IAC? Sounds like its bad and the busted PCV elbow's vaccum leak is doing the IAC's job. Just a thought.

 

Took the IAC off and cleaned it, didn't help. The rubber on the plunger looked a little rough and I don't know if that has any efect on how it works. When it idles in park I get a lot of hunting and surging, 200/300 RPM up to 1500 RPM and then back down, then it bottoms out and stalls.

 

Do a thorough visual on the engine for obvious vac hose and wiring issues, correct these issues, then pull codes if the CEL is on. With the DTC's ("the code(s)") in hand, refer to the diagnostic flow charts that are used by Ford and other professional mechanics, and follow the code resolution sequence. Pretty easy to do. Alldata makes these available to the public at little cost.

 

Remember that there are two elbows on that same line. One to the intake and one the the PCV valve on the back of the drivers side valve cover area on the other end of that plastic line. Maybe when you fixed one it caused enough vac to collapse the other one completely.

 

Not of any help, but I just found my cracked elbow today on my 4.0 I was wondering where you got a replacement?

 

I ended up getting the part at the dealer. Its the entire plastic line with 2 new elbows on it...

These are the numbers that were on the part tag...
KCV-190
4L5Z-6758-HA

 

disconnect the battery for 15 minutes with the headlight switch on to clear the Keep Alive Memory of the PCM. the fuel trims will have compensated for the vacuum leak (rich or positive fuel trim) and it may be getting too much fuel when you put the new elbow on.