2006 F-150 4.6L Rough Idle/Stumble

[RBeach]

2006 F-150 4.6L 4WD - 112,000 miles

Issue: Idles rough once truck reaches normal operating temperature and then has some stumbling on acceleration.

Truck was running fine when it was parked to rebuild rear end. Sat fo about 6-7 weeks with about 1/4 tank of gas.

Parts installed (all were done within last 2 weeks except plugs):
Plugs (last Summer - about 5,000 miles on them)
COP’s
Throttle position sensor
Throttle body gasket (smoke test showed leak)
Fuel pump delivery module
Both upstream O2 sensors
Air filter
MAF inspected and cleaned with MAF cleaner

I have use of a family member’s Matco Maximus 2.0 diagnostic tablet. These are the only off the wall readings I got:

Absolute throttle position B, D and F are in the red, but regular absolute position is fine
Short term fuel trim B1S2 and B2S2 are 99.2 and do not change at all

No injector faults
Power balance test is good
All other sensors show within range

I am leaning towards EGR and here is why: When I unplugged the dual vacuum line and tried to pull a vacuum on the 2 ports, this is what happened.
Bottom port - pulled and held a steady vacuum.
Top ports - I was unable to pull a vacuum. As I squeezed trigger to apply vacuum, needle would barely move and stay around zero.

Any ideas?

[GumpyGrumpy]

G'day, New around here as of today, and I saw your post, about your truck idling hard, and not good when you accelerate. On my 2006 F150 Lariat, I had a similar problem, and I had to replace the fuel module that is on the back axil it sits there, and the underneath of the module rots... and water gets inside it... and so on, she doesn't work no more. So if you go to Amazon, you can order one for about $65, get it, and it's a 20-minute install... After that, it should work much better!

[Dwillhauck22]

Originally Posted by GumpyGrumpy

G'day, New around here as of today, and I saw your post, about your truck idling hard, and not good when you accelerate. On my 2006 F150 Lariat, I had a similar problem, and I had to replace the fuel module that is on the back axil it sits there, and the underneath of the module rots... and water gets inside it... and so on, she doesn't work no more. So if you go to Amazon, you can order one for about $65, get it, and it's a 20-minute install... After that, it should work much better!

I also have a 2006 Lariat 5.4L Triton V8. The issue i am having with mine is that when you come to a stop the rpms drop down into the 300's. This sometimes leads to it stalling out, especially if I just tap the gas and then hit the break right away. If i slip it into neutral the rpms return to the factory range of about 600-700. But as soon as I put it into gear and there is a load on the engine they drop to the high 400 low 500s. I just replaced both the camshaft position sensors hoping they had something to do with it but no luck. One thing i noticed tho is when the truck does stall out the low oil pressure warning lamp comes on and it takes an extra second to fire back up. But after it is running again oil pressure is at normal range. I have an Edge CTS 2 unit so I am able to monitor all of my engines data from fuel rail pressure to intake air temperature and everything in between. Hopefully someone can give me a solid direction to look in so im not on a wild goose chase trying to hunt down the issue http://staticaf.com/vbulletin/images...s/confused.gif

[RBeach]

Sorry for the late reply. The fuel pump module did not work (that was one of the first things I tried). It did end up being the EGR valve. I bought a BWD brand from a local parts house and it was junk. I ended up ordering the Motorcraft one and it solved my issues.