2004 4.6L code p0171 / p0174

[Eddie Lanham]

I can’t get it to go away, I know it is a vacuum leak but I can’t pinpoint it. I also see it is a common issue with older expys, anyone have experience with this problem? And today I found a hose of some sort near the battery dangling, I’ll include a photo in the thread. Also dealing with a loss or delay of power when accelerating. Didnt have that issue until the code came up. Any help is welcome !

 

[RMARTIN]

HEATER VALVE?
https://www.expeditionforum.com/threads/vacuum-line.46171/#post-422488

 

[Eddie Lanham]

HEATER VALVE?
https://www.expeditionforum.com/threads/vacuum-line.46171/#post-422488

It comes out of here and just hangs around the bettery, I can’t figure out where the hell it plugs in to?

 

[Eddie Lanham]

View attachment 40982

It comes out of here and just hangs around the bettery, I can’t figure out where the hell it plugs in to?

Battery *

 

[Hamfisted]

Looks like the other end broke off at the firewall grommet. You should see another vacuum tube passing through the firewall just to the left of the ECU. If that tube you have in your hand is coming off the hot water valve, hopefully the vacuum supply tube that comes off the intake and passes through the firewall to the HVAC control solenoid is still in tact. Does your AC go to Defrost vents when you accelerate ? Take the battery out and you can get a better view of the pass through grommet. Be careful not to crush any vacuum tubes when you put the battery back in.


Tubes passing through the firewall ....

 

[Eddie Lanham]

Looks like the other end broke off at the firewall grommet. You should see another vacuum tube passing through the firewall just to the left of the ECU. If that tube you have in your hand is coming off the hot water valve, hopefully the vacuum supply tube that comes off the intake and passes through the firewall to the HVAC control solenoid is still in tact. Does your AC go to Defrost vents when you accelerate ? Take the battery out and you can get a better view of the pass through grommet. Be careful not to crush any vacuum tubes when you put the battery back in.


Tubes passing through the firewall ....

I’m about to test the acceleration thing right now, so you hit it spot on. I noticed that opening in the firewall where there’s two lines that are broken off and I found the two lines that should be connected, hanging in the engine bay. How the hell do you get in the firewall to fix this issue ? The lines coming from the firewall are too old and dry rotted to splice.

 

[Hamfisted]

Yeah, what happens most of the time is owners just toss the battery into the mount area and accidently crush those tubes or put too much stress on them and they break.
There's not enough tubing sticking out to support just some windshield washer hose to splice the tube ends back on ? If they're that bad you'll have to pull the carpet out of the way and fish some more through the grommet back into the interior right in front of the center console. The control module they connect to is under the dash right in front of the console. You have to pull the console out to access it. It's a huge PITA project. In the mean time you can plug the tee on the manifold to stop the vacuum leak there and get rid of your 171/174 codes till you get it fixed. It comes off the driver's side area of the throttle body. Just put a cap on the vacuum supply Tee.