I'm trying to step through some of the fixes for a p0171/p0174 code I've got on my truck (1999 f150 4.2L) I've replaced the fuel filter, now I've replaced the pcv valve. I can't (or have not tried hard enough?) to trace the hose that is connected to this valve, so I can check for leaks elsewhere. I plugged it in to the elbow as was originally but can't seem to locate where the hose is running off to across the engine. I hear a hissing sound as the engine is running, and also there is a significant hissing/sucking noise as the engine cuts off, that last for just a few seconds longer.

Any guidance would be appreciated.
Thanks,
Greg

P.S. Great web site

 

Hi Greg and welcome to FTE

How I usually find vacuum leaks is with a can of Carb Medic spray carb cleaner or something similar. With the engine idling you spray the cleaner at the different areas where there could be a vacuum leak. If the idle changes either up or down when you spray it you've found your leak.
Another common cause of the codes you've got is a dirty MAF sensor. You'll find instructions for cleaning it in the FAQ's at the top of the forum.

 

Well I found the leak, even though the spray method never helped (I probably never got the spray back to it).
The leak is on the very back side of the middle hose that is just above the pcv valve. not noticable until I actually ran my fingers all along the hose as someone else had suggested. Now my question is...
How does this hose come off!!
I pulled on the part that runs into the back of the manifold, but it will not give. I know that I'll be able to get the other piece off the pcv valve.
Do I just pull real hard, or do I need to set some time apart and begin to take things off of the engine, namley the hood. Cause that darn little hose is in a very hard to reach spot.
Any inputs appreciated.

 

You know what. I ended up finding out that the entire vacuum harness had to come off just to replace this one piece. The harness was around 35 dollars and the job was relatively simple with a little patience and few common tools. I don't remember all the details except that it was the fix. I spent maybe an entire hour from start to finish, probably could have done it quicker if I already knew what I was doing.