I have a 2001 f150 4.6l 4x4 fx4 5 speed manual transmission with 160k on it. A couple weeks ago I developed a problem where my engine when I would shift to neutral would rev up to around 3000 rpm's stay there for about 30 seconds then drop down to 500 rpm's and fluctuate up to 900-1000 then back to 500 like it is going to stall. I dont notice any sputtering when I'm driving other than it tries to rev up. The check engine light came on so I took it and had the code read and it said it had a to lean air/fuel mixture and two O2 sensors were faulty so I replaced all four figuring it would need eventually. This didnt help, I took it back and it said theaks mass air flow sensor was bad so I switched it out and it to didnt fix it. I took it to the ford service department and they said i had a collapsed intake manifold line and could fix it for $324.00. Anyone heard of this, and where this line might be? Thanks for your help

 

It's a vacuum leak by he sounds of it. If I was a betting man I would bet it is the PCV line

 

yeah, probably that pcv elbo on the back on the intake manifold that jbrew has a picture of.

 

Yea , which view are you looking for ?

Here's the most common view I post , the elbow back by the firewall is the one that usually goes out. I'm surprised you don't have a check engine light on with a problem like yours.

The problem can be anywhere in the PCV system , even the valve itself. Also, one of clamps may be loose on the air intake. So check everything.

 

Check engine light is on, code said it was a to lean fuel mixture, bank one and two, but ford dealer said it is a collapsed line. I will check that elbow, thanks

 

a collapsed line lol... yeah its prolly that one in his picture

 

Yea , the only line I ever seen collapse besides a brake line is that EVAP line on top of my 98 (fuel vapor hose)- but that was because I had my system hooked up wrong.

The vapor line is the top line on the throttle body elbow in this pic. I seriously doubt you have this problem unless you have hooked it up differently -

 

Thanks Fellas for your help. Jbrew it is that elbow back next to the firewall, it has a hole in it or something, I can reach back and put my finger on it and feel the suction, when I cover the hole it runs fine. Next big question, how the heck do ya get to it. Do you have to pull that whole assembly? And what is that elbow called so I know what to ask for when I go get it. Thanks again, thats gonna save me a bunch. Those fellas at the shop didnt even put the thing on the computer I bet, spent $70 for nothin.

 

Yea that's it. I use a long handled needle nose pliers w/90 degree bend @ the end to get that one. Sometimes there stuck on there pretty good. If you have a replacement, you can use a long screw driver and pry it off. I can get back there with my hand, but can't always get the damn thing off once I worm my way back there..You'll get it

 

Will they carry that elbow at a local parts store like advance or will I need to get it at ford? There are two lines coming in to that elbow right?

 

Huh? No , this elbow - I circled it for yuh