I replaced the Mass Airflow sensor last Spring. Around March when it was still a little chilly in the morning my 01 F150 5.4 started idling rough and I went to Autozone and had the code read. I do not remember the codes now but it required replacement of the MAS. It ran fine after but it was not chilly anymore either so the conditions changed.


I know I am putting the cart before the horse here, but this morning the Service Engine light came on again and its running rough at idle again.


I know electronics can fail and this MAS was brand new and should last more than 8 months. Could it be something else? Should I try to clean it first? I will try to get the code read sometime this week, I was just looking for different scenerios it could be before I paid another $100. I hope this is not a yearly thing. I think I put a Cardone brand in it from rockauto.


Any suggestions? other than get the code read.

 

Why are you not getting the code and acting on at code instead of trying to second guess?
You likely never needed a Mass Air sensor the first time.
Good luck.

 

Wasn't really trying to second guess was just entertaining ideas or what may have caused the issue to begin with. But I got the codes read and it is the MAF again and an O2 sensor this time. Last time it was the MAF code.

 

We need the codes for our interpretation, not some ones else's because they are often wrong.
You already have been through that and has not been the fix..
If you came here for help fine, asking others to guess does not help anyone.
Good luck..

 

Understood and not trying to pick an argument. I should have waited til I got the codes. It threw a PO1071 and 1074. Im curious if the MAF go out that quick if that is normal of if I have another problem somewhere else causing it to go bad.

 

You prolly mean P0171 and P0174.
Look for a vacuum leak.
Especially at the rear of the intake manifold.
Where the PCV elbow lives.

 

Now you see why I replied as I did.
There is no 1071 or 1074 code but there is 0171 and 0174.
Neither is a fault of the Mass Air sensor.
You have an air leak that has shifted the fuel tables too 'Rich'.
This has caused the codes to set for both banks because the fault is common to both banks.
Good luck.

 

I looked today and could not find anything obvious. I checked the PVC hose and the best I could behind the engine. Wouldn't it run rough all the time if it was air leak? Im not doubting the information just curious. Right now it only runs rough when its cold out in the morning. Once the outside temp gets around 40 or above the truck runs perfectly. Below 40 and it is rough idle. Once RPM are up and you drive it runs fine. Until you stop at a light and then it runs rough again.

Sorry about the code confusion. I wrote it down right and translated to the keyboard wrong

 

I am in doubt we have enough accurate info at this point.
Take another look at the codes and be accurate in there numbers.
I don't want a description of what you think they mean because I know what they mean in a technical sense..
.
A cold start and rough running until warm up indicates some other issue.
An air leak usually does not show up on cold starts but does after full warm up as rough idle and stalling.
Until we get specifics pinned down, we don't know what direction to go in.
Codes first, then we decide where to go from there.
You may have two different issues at the same time.
Good luck..

 

A contaminated or defective MAF sensor can cause a P0171/P0174 code combo although vacuum leaks are, by far, the most common cause of that code pair. See TSB 04-17-4 for instructions on how to diagnose as well as TSB 01-9-7 for a more in-depth review of how to troubleshoot this concern.

Hard starting and rough running when cold are also common symptoms of a vacuum leak.

Inability to maintain engine idle control is also another common symptom of a vacuum leak.

All of these symptoms have multiple possible causes so the above doesn't mean you have a vacuum leak, but the symptoms strongly suggest it's likely.

 

The correct codes are P0171 and P0174.

This is exactly what it does. Cold start outside air temp under 30. Truck starts just fine and runs perfect for about 10 to 20 seconds and then as high idle starts to let down it runs really rough. I let it run at least 5 minutes before I leave for work. On the drive to work it runs great until you stop and it idles. Sometimes it dies at the stop light sometimes not but it idles really rough. When I get back in it about 2 hours later after being at work it runs fine, no rough idle. By this time the air temp outside is above 40. It will run fine the rest of the day.

I will look again tomorrow for vac leaks and double check everything I looked at earlier.

 

Ok, you simply have an air leak you have not found.
For the way you describe it here is why it does what it does.
0n cold starts the fuel is very rich, the ignition timing is advanced and the IAC is open to allow more air with the rich fuel.
.
This covers up the air leak effects.
As the engine warms, the OX sensors take control of the fuel, the fuel leans out,
Idle comes down but you still have the air leak that has shifted the fuel tables richer than they normally runs at.
This hurts idle and low speed drivability because the Ox sensors detect the air leak and keep the tables shifted rich trying to 'counter' the air leak, causing both codes because the trouble affects both banks.
I would still bet on the PVC ELL on the back of the vertical intake manifold that feeds right into the intake system.
I've been there, seen it before.
A Scanner looking at the long term fuel tables will show them shifted more than 25%, proving the cause.
Good luck.

 

Thank you for the details. That explains alot to me. I will look again and go over each line with more detail this afternoon and report back.

 

I am kind of at a loss at the moment. I did not check it before while it was running, I just checked hoses at first for obvious rot or cracks.

Today I did it while it was running. I can hear a very high pitched scream coming from the area around the PCV valve but not the valve itself. I spent 10 minutes trying to locate the exact location and cannot. If I did not know better I would say it was COP or the injector. It sounds to me like that area. I wiggled them as it ran but the pitch of the scream did not change. But the scream sounds like a air leak. As the RPM changes the pitch changes. Here is what I tried-

All while truck idled-

Unplugged the PCV hose and plugged it with my finger. No change in pitch as I toggled my finger off and on.

Unplugged the red/white/black lines off the throttle body assembly with no change in pitch.

I removed PCV valve from the valve cover and again no change in the pitch.

This is just a guess but could it be a cracked manifold? Or would that throw a different code and I am in left field with my thinking.

Any thoughts? I could try to video it and upload it if that helps.

The PCV hose and elbows seem to be in pretty good shape, they are still soft and pliable, not hard and falling apart. I have not tried the trick of spraying carb cleaner or something flammable around it yet to get the idle to change at the leak. Parts store is closed today

 

If this helps

VID_20151220_141553946.avi