Hello there, I have a 1997 f150 5.4L and recently the check engine light came on. Took it to Firestone and they told me that the engine is running too lean and it was intake manifold gasket leaking. This is he third vehicle they said that to. My dad took a look at it and he saw that the vacuum hose is collapsed and there was a hose that was just hanging there. We reconnected it and at idle it's rough, and shakes real hard as if it wants to die but when you give it some gas it smooths out as if there's nothing wrong. So before I rip out the top end of the motor to replace the intake manifold gasket, could the problem be the vacuum hose or something else?



The vacuum hose





The hose that was hanging there that isn't secure

 

I hate to even get involved in such a thread where total incompetence is being displayed but decided to try.
First; stop what your doing.
The shop you are using is incompetent to work like this and you have no base line knowledge to work from.
The shop never told you what the codes were and you should have asked.
Lean codes are P0171 and 174. Is that what is set?
They do not point to tearing the intake off 99% of the time.
You do have an intake system air leak that is causing the lean codes to set.
.
The collapsed hose does indeed need replacing. Vacuum has sucked it closed.
The open ended hose may belong to a port on the same hardware below the Green connector. I can't quite be sure from the angle of the photo but that connector should be White. Is it there?
Find the proper home for that hose, replace the one with the green connector, then lets go from there.
While your at it inspect the hose from the passenger side of the valve cover to the rear of the intake. At he rear there is a Rubber Ell that very often goes soft or hard and admits air.
This fault will cause rough and stalling idle after the motor warms up.
I hope I have not insulted you but needed to run up the Red flag on this one to even try to be of help..
Good luck.

 

It's not that I'm incompetent, my dad was the one who had the truck at the time. I live in New Mexico and my dad lives in Houston he was bringing the truck up and the day before he brought it is when the check engine light came on and he took it to the shop. He was the one who told me what the shop said. I wasn't there to ask any questions. I'm simply just relaying what he said. I just wanted to see if what Firestone said was valid.

 

The vast majority of the time the lean codes are vacuum lines usually PCV system. The elbow at the back of the throttle body is the usual source.

 

I would hope you understand my reply is based on what your post contained.
I have no idea what the past is, who was involved, when or why.
You just need some competency (in the whole scheme of things) to get the truck repaired.
I do not expect you to be at this level but just informing you about it from all that has gone on so far, because you came here to ask.
I cannot smoothen this over and tell you something different because it won't help solve your issues.
It may not sound like help but it is a start you need to begin from after being lead astray..
Good luck.

 

Bluegrass,
Any input on how to see the elbow behind the throttle body. I took the truck to a shop where it was inspected OKed . Before I tear into the manifold gasket on a 2002 110K truck ...how do I see it myself? Trust with verification.
Regards!

 

It's tough to visually see behind that vertical manifold without using a mirror and light.
The hose pulls crank case fumes from the PCV back into the engine intake.
The fumes softens the rubber and eventually sucks a hole in the soft part.
This becomes an air leak.
Assuming all other hoses are in their proper place and none of the modifications I see listed are causing an issue, hopefully there is only one air leak and not more than one to confuse.
A way to test for a leak in that area is to uses a flammable spray cleaner sprayed in that area with the motor running.
If there is a hole, it should pick up some of the spray and change the idle speed.
Another way to check for a leak with spray is to look at the short tern fuel trim tables with a Scanner for a change as the motor picks up or senses the spray.
Best I can offer for now.
Good luck.

 

Thanks Bluegrass!
Heading outside to check with some carb cleaner.