ok I just put this thing in and learned something the hard way:

the hard plastic tube that goes into this elbow runs underneath the intake manifold and joins into the PCV behind the manifold where the other "bad" elbow is. The PCV is T'd off in about four different directions.

Im mentioning this because I accidentially pulled the tube out of the T and it was really hard to put back in. I couldnt see the fitting and had to do it all by touch, its very tight back there and theres some kind of hose clamp that cut my hand.

Be very very careful not to pull the tube too far when changing the front elbow or you will be having a not so fun afternoon.

however my idle is 100% back to normal and 100 miles later no "check engine" light

 

I have seen the fuel system treatments burn up o2 sensors if done incorrectly. I actually did this one drunk night with my Lexus. I ran the cleaner through too fast and fried a couple o2 sensors. Not definite, just saying it's possible.

 

I think it's fixed... This thread is over a year old.

 

Just fixed my 2000 F150 V6 w/ 209,000 miles that's had P0171 & P0174 codes for a few weeks. After cleaning the MAF and installing a new fuel filter, I got the codes back (after clearing). PCV hoses on the passenger side valve cover seemed fine, but I found a disintegrating "formed" gas/fuel hose from a metal elbow under the throttle body to an evap valve on the driver side firewall (next to the brake booster). Dealer wanted $65 just for that tube, but I replaced it with 24" of 1/2" ID gas/vapor/PCV hose for $6, but the codes still came back.

Finally today I found the rubber PCV elbow just behind that metal elbow under the throttle body was hissing when using a 1/2" flexible tubing as a stethoscope (poking around under the intake manifold). It was hard to see, but I could finally see a dimple in the outside part of bend, and after removing it found a good-sized hole there. It had degraded/thinned from the inside, then finally a hole formed.

Ford dealer only sells the elbow in an assembly with the PCV valve and plastic tube for $65 (seems they want $65 minimum for anything), but I found an exact replacement PCV elbow at O'Reilly auto parts in the "Help!" parts section (part #46022) for $10, and it looks like that was the main issue throwing the codes

Here's the damaged elbow with the packaging from the replacement:

 

The PCV elbow leaking is a pretty common problem. I've replaced 2 so far in the 6 yrs I've had my truck.

 

Hi all, I'm new here, and I know this is an old thread but.. I just wanted to say thanks to tap4154.

I went round and round looking for this air leak, and that description above helped me find it. I was searching for info about doing the intake gaskets, and it led me here.

12 dollars, and 15 minutes of work later, and the problem was solved! I love it when it's a simple fix..

 

I had this problem on my 03 xlt 4.2 with a 152k, I went to o'reily's and they had both the bolts and seals. Took my step dad and I about 5 hours and a lot of carb cleaner but that fixed my p0171/p0174 codes. But I am still working on my misfire on 1, the journey continues. Hopefully this helped, I have done a lot of looking around and I just wanted to put my testimony out there because I know this is a huge pain. Cheers.

 

If the misfire is only on #1, then it must be electrical right?

Mine is a '98, and I had to replace the coil pack at about 175-180K iirc. I had a hard misfire that caused the check engine light to flash, and it happened "all of a sudden". I started by just replacing the plugs and wires, but the new coil pack is what solved it.

 

Yes I ended up pulling my coil pack off to find three huge cracks right under each coil. Replaced with motorcraft coil pack and plug wires, runs like new. Yes another good look see for all of you 4.2's with issues.

 

waddya talkin about?... Dead horse???

My baby runs fine still. And't it's been a while since she needed surgery. iirc, that vucuum line was the last thing I had to fix, and it was a cheap fix once I found out where it was.

The 4.2 might not be the fastest machine out there, but I'm happy with the reliability..