Okay guys, here's the story. PCV was replaced when I bought the truck, checked it anyway and it's fine (including the hose). Had a bad fitting K&N filter that was allowing the MAF to get dirty months ago. Found that out when I had my mechanic fog test it. He said that the filter was really the only thing he could see. Codes went and stayed away until the other day. P0174 came back and this morning, one of the coldest we've had in a good while, I had rough idle at stops. RPM up then down. You know how it goes. I am honestly tired of these codes. I've noticed my gas mileage drop some and she just doesn't have the pep in her step that she usually does. Does anyone have any ideas? Video and pic posted below.

Reason I posted the pic, and yes I know my bay is pretty nasty, but there is a lot of build up on the passenger side cover...seal leak???? Or is this pretty typical? Haven't cleaned the bay since I bought the truck in '09.

Here's the video.

 

P0174 is lean bank 2, which is driver's side. Vacuum or intake leak somewhere, or possibly an exhaust leak on that side.

Nasty idle can be a dirty IAC.

 

Forgot to mention that I also replaced the IAC last year. Idle is only rough when cold it seems. Makes me think gasket.

 

These things are tough. I am currently having a similar issue with my Expd. I had a whistle along with mine. I cleaned Mass Air, replaced PSV, IAC, and EGR along with associated plumbing including the vacuum silencer. I have a feeling it may be an intake manifold gasket. Is currently at the dealer to see what they can find. Here is a pretty good write up I found.

http://www.fordf150.net/forums/viewt...65607&start=15

 

UPDATE:

Emptied another can of carb cleaner this afternoon looking for vac leaks. Again, I found nothing (not that I really expected to find anything). Crawled under the truck and double checked the exhaust. Aside from a littler surface rust there were no noticeable leaks that I could see or hear. Does anyone have any other ideas? I feel like I can hear a leak somewhere from under the throttle body but it honestly may just be my imagination hoping for an easy fix leak.

I reset the PC yesterday and cleaned the MAF again, did not get the light back on today but didn't drive at highway speeds so I don't think the monitor has cycled yet.

Just to clarify, the rough idle is something that does NOT happen all the time. That's why I haven't worried about it too much. But when it did happen the other day, it was something similar to when my IAC went out/clogged up. Truck did not die but the pulsating idle just makes me want to figure this out. Hate it when my baby's sick. I haven't gotten any live data on the CE codes, but honestly don't have the equipment to do this. May ask a local mechanic to smoke it again to rule out any big vac leaks just to put that bug to bed.

 

Need help check engine light been on getting about 260 miles to a tank. Took it to dealer and did a tune up,reprogrammed the PCM,replaced the fuel pressure sensor.now the dealership told me that ford to make the trucks lighter they decided to put plastic air I take manifold and they believe that it's got a leak. Truck runs perfectly fine but horrible gas mileage and idles rough.please anyone with any ideas running out of patience and money! Already spent close to a thousand dollars and now they want another 970$ has anyone had this problem

 

There are a ton of threads you can search for. What, if any, codes are showing?

 

Dealer finally got the truck to whistle and found general area, and smoked it. Looks like intake manifold leak. Hopefully gasket possibly cracked intake. Will not know until they pull it apart.

 

Double edge sword. Glad they possibly figured it out but hope it's not a cracked manifold.

 

Hopefully gasket, price doubles if it is the intake. Really wish I had the time to do it myself. Three girls, and working 55 hours a week doesn't lend itself to be able to get anything done in a reasonable time.

 

I have this exact same problem and I planned on cleaning the throttle body. I, too changed PCV, IAC, DPFE hoses last year, but my idle is bad on cold days. I had the same problem a couple years ago and it was fixed when I had Valvoline run their full fuel system clean. You wouldn't believe how much black came out of the tailpipe... I plan on having them do it again very soon and hope that helps... I will check my intake manifold though...