2006 F150, RWD, 4.6L, Supercrew

I seem to have a sudden misfire condition similar to the last time I had an coil failure. When I went to have a look under the hood, I noticed this tube hanging there. No clue what it is or where it goes... can someone help me out? The rest of the wire bundle goes to the fuel rail pressure sensor on the driver side. The end seems too clean to have always been there and I don't ever remember seeing it.

Any help would be greatly appreciated!!

 

That a vacuum line for 4WD.. just zip tie it up out the way. What the mileage on your motor ? Maybe time for plugs/boots and springs.

 

Okay great, thanks!
I'm over 150k miles. I did all the plugs and 2 coils when I had a misfire last year. Kicking myself for not doing it all the first time.

 

If i were you.. I would replace all the boots and springs first... coils normally set a code when bad.

 

To update this thread and bring it to closure.
Misfire was happening on Overdrive only under load.
Changed boots and springs on 6 remaining cylinders which looked original. None appeared to have any evident/obvious problems.
Misfire gone.

 

You should replace your spark plugs.

 

Nice !

 

I thought the issue was gone, but I was wrong. It may be improved but there is still something wrong. I have what feels like a slight misfire at low rpm (overdrive) and I have noticed a bit of a rough idle.

Ran Mode 6 diagnostic. No misfires found but I did fail TID $82.
Value 0.447kPa
Min -32.768kPa
Max -32.659kPa

Test was run at idle. EGR valve issue? I checked the tubing and didn't see any cracks and everything is connected. I blew out all ends with some compressed air.

Any ideas or things I can try? Other EGR diagnostics seem to have passed.

 

According to the Motorcraft OBDII Theory of Operation Manual (Page 47) - your Mode 6 TID $82 is the A/D converter value being read from the Differential Pressure sensor for upstream hose test.

I READ _SOMEWHERE_ "that that specific TID report had the incorrect 'MIN' & 'MAX' programmed in certain PCMs causing the Mode 6 report to erroneously report 'FAIL'. ((BUT I'll be damned if I can find it again in spite of searching hard for it)). The Forum search engine is pretty lame.

But it actually makes sense. Where minimum and maximum readings are programmed in for benefit of Scanners to compare for error - what reading would ever have a minimum and maximum exactly the same? You have nothing to worry about from that 'FAIL'.

Although I would add that I do not authoritatively know if your actual test reading of 0.447kpa is OK. I am inclined to think it is NOT, and if I am right could tend to aggravate misfires. EGR valve Differential pressure being a measure of exhaust gas recirculation flow - too much will dilute combustion gases. You might investigate further, remove and cean or replace EGR vave.

BTW, If you do not have a copy of the OBDII Theory Manual for your truck you can download a copy for FREE from here: https://www.motorcraftservice.com/freeresources/obd

Select Country, then from the tabs at top Select >Free Resources, >OBDII Theory & Operation, > and select Your vehicle model. It is a GREAT resource.