Hello, I've been a lurker for a while and finally have a problem. I have a 98 f150 v6 engine build date 3-18-98 throwing codes p0171 + p0174. I found the elbow under the IAC to be bad and the one connected to the back of intake near pvc. I bought that whole setup at dealer and was a upgrade they said. The rubber tubing was hard as a rock and plastic tube was very stiff comparing new to old. I also read about tubing behind the battery to be bad for some and I could brake those rubber tubes down with finger nail like they were chalk. I hope the new rubber used is much better quality. I have 89K on this truck which means these were probably bad at 50k. My question is where are the other elbows/tubing located?

I read a lot yesterday but so tired and forgot to save some good post. I believe there to be some more connections located in the middle a foot or so down close to firewall which is about where I was hearing hissing before. If it is such a pain to fix in this location as I believe it will be maybe I should pull the intake and change gaskets/isolator bolts. I know from TSB my engine build date has newer gaskets. Would you go ahead and change them?

Another thing is I can't seem to pull tubing off either end of new rubber long tube so I can thread it under intake back to pvc. It's like it's epoxied on on both ends and rubber tube is as flexible as a straw. Maybe I can figure out what else I can disconnect from the side of intake so I can fit it in from the side.

I could simply lay it down before re-installing intake if I should replace upper intake gaskets. I hope I haven't said too much for anyone to bother reading.

 

fixed the same codes by cleaning my MAF sensor wires, I took it out and used MAF cleaner. been 12k miles since, no codes.

 

I will clean MAF after I fix vacuum lines. It's very obvious vacuum lines at this point.
I finally had the time to figure out why I couldn't break my post down to paragraphs(no script) with firefox. Grass mowing done for a week:P

I wish I didn't have such a bad memory. I could swear I didn't have any oil leaks before this but after moving around under truck and seeing a few with trans/motor connection and maybe lower intake a little bit maybe I shouldn't had drove it after lean codes. I dunno what post made me think it was ok to drive if i didn't have to.

I will change spark plugs/wires(motorcraft), run some cleaner through injectors, already changed gas filter for 3rd time, air filter again(because fram's making bad connection), clean MAF,TB, IAC if i can. Flush coolant.What I've read I need a upgraded valve cover so, so much oil isn't blown into intake breaking down isolator bolts.

If I knew how I'd post pics of new to old tubing from IAC to pvc/intake and location of connection to intake. Do I need to use external picture sites or use this site and what size.

 

Advise repairing for the codes first then do the other work.
If you get into trouble, then you don't have more then one issue to cause confusion.

 

Yeah, I'm not doing anything else until I fix vacuum lines.
I'm wanting to know if there's more vac. lines mid way down near firewall I need to be concerned about?
I read something somewhere. Something about some bushings included and a bar of some sort.
Time to re-read a lot and save something this time.
Thanks

 

There are lines that feed to the canister purge solenoid, they are not part of the main vacuum tree, but they can crack and split or the solenoid can leak. The other lines feed to the brake booster and air conditioning controls etc. Those can crack anywhere along the length or the vacuum motors can rupture internally. The brake booster can also leak internally. However, none of these problems are as common as leaks at the elbows. Most of these problems are easier to diagnose because they can cause other components to malfunction. If your blend door works correctly, and the brake booster operates, then those parts and the lines feeding them are probably ok.

The other possible issue is a leaking upper or lower intake gasket. When those gaskets fail, they can be difficult to pinpoint.