I have an 04, 5.4 with 78000 on it. The other night I started it and it was almost as if I didn't keep the key turned long enough for the engine to catch. It shuddered and let out a loud pssst sound. It sounded as though the engine was releasing all of the air it had taken in. The cab was immediatly filled with a strong exhaust smell. The truck started right back up after this. Seemed to run fine on the way home. The next morning the truck seemd to have a rough idle. That night it stalled as I sat at a red light. Now, if I do not feather the gas when sitting at a stop, the truck idles a little rough for about 25 seconds and then stalls. No codes and the truck runs great when driving and not at an idle. Any ideas??

 

Could be the idle air control valve. Just replaced one on my '00 Expedition w/120k miles. It was similar to this, fired when turning the key then stalling, stalling at stoplight, etc. About $60 for the part and 10 min to change.

 

Iac!!

 

There is no IAC on an '04+ F150, idle speed is controlled by the stepper motor on the throttle body.

 

I had finally gotten some codes P0141 & P0142. I disconnected the battery to clear the computer. Today I was driving and got a check engine light again. I'm expecting to see the same codes but now it reads Lean Bank 1 and Lean Bank 2. Truck continues to idle rough and stall at an idle once it is warm. I guessing that the spit and sputter/ backfire as described in my first post damaged something. Any ideas what it damaged? Help! Codes have changes and truck still runs horribly!

 

Lean codes from last post are P0171 & P0174.

 

A code P0171 may mean that one or more of the following has happened:

- The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters (K&N, etc.) can cause the MAF to become dirty if the filter is over-oiled
- There could be a vacuum leak downstream of the MAF sensor.


Possible solutions include:

- In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
- Inspect all vacuum and PCV hoses, replace if necessary
- Check for a dirty fuel filter and proper fuel pressure

Source: http://www.obd-codes.com/trouble_cod...gen-sensor.php

 

Driving today and the 4X4 tries to engage. Sound like a blender with ice from the front end. I flipped the switch into 4 high and back to 2wd and everything was Ok. I'm wondering if this could possibly be a computer issue effecting the 4WD and my idle when warm. I saw TSB (05-5-15) regarding reprogramming the PCM when there is a rough idle. Could this impact the 4WD in any way? In the last 2 days I have checked MAF, all vacuums and gaskets. I am really at a loss as to why I have a rough idle. Well actually a rough idle and then once the truck is warm it stalls when at an idle. Runs like a champ when cold or at highway speeds. Anybody ---HELP!

 

There's a vacuum hose under the driver's side rear of the intake manifold that rots through on higher mileage 5.4 3Vs. The easiest way to get to it is to remove the intake manifold, but if you're double jointed and got a strong arsenal of four letter words, you can snake the hose in and out from under the truck.

 

First off, thank you to all who have replied. After almost a month of working I have solved nothing. Basically, the truck runs fine cold and on the highway. Once it is warm, still runs great on the highway but will stall at a stop. Codes still read P0171 & P0174. The Rpm's are up a little and drop right before it stalls out. I sprayed and checked every vacuum line. I even pulled the intake manifold and check the line below it as suggested by Quintin. I cleaned and eventually replaced the MAF. Ford had it for about 5 hours and cannot find anything. Don't worry though, $150 for diagnostics. When I asked what the diagnosis was ----drumroll---for $150 they told me it is running lean on both banks but they weren't sure what is causing it at this time. 30 seconds on a code reader can produce this diagnosis! Anyway, it seems to have the symptoms of a vacuum leak but all hoses and MAF are good. Any other ideas as it looks like I am on my own here. Is there anything that could have broken during the backfire/exhaust smell incident that started all of this? (see first post in this thread) One thing that I forgot to mention in the previous posts was that after the backfire, the front hubs were like half engaged. It kind of sounded like ice in a blender. I flipped the truck into 4X4 and back out and it has never been a problem since. So, when causes a spit , sputter backfire, 4X4 to half engage and codes P0171 & P0174? This is the mystery that I cannot solve. Any other ideas greatly appreciated. Thanks again.

 

Shot in the dark here, but could the backfire cause some destruction to the O2 sensors?

 

My '00 5.4 started doing similar things this morning. It fired up and immediately stalled. Did this 3x until I finally feathered the throttle to keep it alive. After a few minutes it would hold an idle and I was able to putt away to work.

Leaving work this afternoon, same thing. Until the truck was fully warmed up it'll sputter around. I initially thought it could be the fuel filter or IACV but this thread seems to suggest that it's the valve.

I'm replacing the fuel filter and spark plugs this weekend; I'll see how that goes.

 

Thanks for the new input. I'll check the O2 sensors this weekend. I'm gathering from reading other posts that the two to focus on would be the upstream sensors.

 

Thanks to all who gave input. It turned out to ba a bad vapor management valve. When that was replaced, problem disappeared. Thanks to Quintin who actually pointed me in this direction when he replied to another member who was having a similar problem. After much work and frustration, the F150 is back.

 

My 2000 5.4 is doing the same thing. Started out doing it every now and then but now it stalls every time I start it. I have to feather the gas to get it going. I've cleaned the TB and it was fine for a while. Now that it has return I cleaned the TB again and it didn't seem to help. I tried to remove the IAC from the TB to clean it or replace it but can't seem to get the screws to turn. It is mounted to the right side of the TB with two brass looking screws right? I started stripping the head of one so I stopped.