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Discussion Starter · #1 ·
Hello, please help with an issue that's driving me crazy. My 1999 4.2 litre is showing fault codes p0171 and p0174, likely a vacuum leak. One of the common issues is the valve, tubing, or elbows in the pcv system. I want to remove the hoses and the valve from front to back in order to inspect properly. The pcv valve is on the valve cover, passenger side, and the hose goes: a)to a Y connector that leads to a connection near the fire wall and b) behind the intake manifold where it becomes impossible to follow. I've tried lights and mirrors to see where the hose goes but things are so tight behind the intake and so close to the fire wall that all I can make out is an elbow and then I cannot follow it further. Can anyone tell me where the end of that hose goes (where the gases are re-introduced into the intake) so that I can disconnect things at the pcv valve, the end of the Y connection, and the 're-introduction end', remove the whole apparatus and inspect everything without tearing apart a bunch of stuff to get at it? Replacing the pcv hose is shown at .3 hours in a '99 f150 labour manual, and so I'm thinking that it shouldn't be that hard to do but I'm a loss. If anyone can point me in the right direction, I would greatly appreciate it. Thanks.
 

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I have no clue .. but if having no clue and wanting one , I'd go to the local pick N pull auto wreckers and have a look see on something that might not matter if I pull some of it apart just to see how it's put together

this has worked for me before
 

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Discussion Starter · #3 ·
Hi I Like, I solved the mystery. I found a pic of an intake manifold and some hoses lying on a workbench (www.f150forum.com/f86/1998-plenum-coolant-lines-263057/) and determined that the pcv hose system was identical to mine. So I deduced where it would go and sure enough, found the elbow end where it goes back into the intake (under the throttle body). I took off the throttle body cover and air intake housing to get at the rubber elbow that is notorious for developing holes and causing a vacuum leak with resulting fault codes. Guess what? It had a hole. So I did go to a local wrecker and managed to find an identical elbow in a totally cannibalized f150 (the elbow was in good shape; the f150, not so much). I put it on this afternoon and will see if that solves my problem. Driving around with the check engine light on is frustrating!! Thanks for your input.
 

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Discussion Starter · #4 ·
Hi all, I just wanted to update everyone on my issue. When I put the elbow on I cleared all fault codes (p0171, p0174, and p1131) and hoped my problem would be solved. 3 days later the "service engine soon" (ses) light came back on. This time the only code was p1131. My research led me to believe that the vacuum leak had been fixed by the new elbow (no more p0171 or p0174) but that I had a problem with the upstream 02 sensors (p1131). So I ordered two new 02 sensors from Rock Auto in Wisconsin. Interestingly, the two sensors together only cost $64.70 Canadian, including shipping right to my mailbox, whereas I understand they would have run about $70 each, plus 13% taxes, at Canuck Tire. Go figure.

Anyway, I had to borrow an 02 socket from my brother to try and get the old ones off, and before I got the chance, the ses light went off on its own. That happened about six weeks ago, and it has not come back on. So, crossing my fingers: a) my problem appears to have been resolved by the new elbow alone, b) I have two brand new 02 sensors sitting on a shelf in my garage! However, if my problem is indeed licked, considering that I wrestled with it for over a year, all the while fearing a more serious issue like lower intake manifold gaskets or something else expensive, I will positively state that that $64.70 is the best money I ever wasted!!
 

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Give it a bit, your waste may not be in vain.
 

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Discussion Starter · #6 ·
Hi again everyone, while this thread is now old and stale, I thought I would update it anyway. I got no fault codes for the balance of 2017 (I park the truck in the winter) but shortly after putting it back on the road in the spring of 2018 the SES light came back and showed a P0133 (pre-cat 02 sensor trouble) and so I tackled putting on the sensors I had purchased from Rockauto back in the fall of 2017. Turned out to be an awful job; the originals were almost welded in place and I was afraid to strip the bolt heads. So I broke down and went to my brother-in-law's garage, put her up on the hoist, removed both front tires and the splash pads, and he took the torch to those 02 sensors. The unit he had reminded me of those flame throwers you can see in WW2 documentaries. Anyway, he got the 02 sensors red hot and they came out. We put in the new ones and for the rest of 2018 the truck threw no new codes. I parked it in late October and will get back on the road in April. I'm hoping the issue is now permanently resolved. Destruction, you were right about the Rockauto purchase not being a waste of dough.
 
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