What does this mean and what should I look at first? My sevice engine light is on but the my 2003 F150 runs fine...but 2 months ago I did have some problems. One time it stalled halfway out of my neighborhood so and everytime I started and I put it in drive it would stall on me but when I put it in reverse I was able to drive it back to my house in REVERSE...I let it sit for a couple of days and it drove fine after that but still took it in to get checked and they said there were no problems and resetted my codes. But since then the service engine light keeps coming back.. I have had a couple of rough idling days but it happens very rarely. Someone told me that it could be a bad MAF sensor or a leak at one of the valves or hoses connected to my Air Intake... where is the MAF located at and how do I find a leak?
ANY HELP WOULD BE APPRECIATED MY FRIENDS!

 

Hi and welcome to FTE and the 4.2 / 3.8 Forum. Glad to have you here.

Here is a related thread:
https://www.ford-trucks.com/forums/8...-me-crazy.html

You can also use the search funtion on the tool bar up top to find more info on P0174.

Common causes:
Vacuum leak
Dirty MAF sensor
Clogged EGR ports

The MAF sensor is located in the intake tube, just past the air filter.

 

Check the rubber elbow under the upper intake. It's conntected to a hose that gose back towards the firewall. You can't see it very easily so you'll have to look close. Anyway... thise thing dry rots. I was throwing a P0171 AND P0174. Drove me nuts. Had some of your symptoms but they got worse. Turned out I had about a 1/4 inch hols in the bottom of this thing. I paid $13.32 at the ford dealership. Though it took me pulling it off the truck and showing it to the parts guy before he could figure out what I was describing. I hope this helps.

 

Everybody that has a 4.2 is eventually gonna come up with this problem..... it is rarely an easy fix such as PCV, MAF, or vacuum leak... although you may have these problems too fixing them will only drop the code for awhile... it will be back

here is the fix!!! (this is the best write up Ive seen)
Welcome! ?(Ford F150 P0171/P0174 Fix)?

 

Nice info!

Thanks Paul. Hopefully this will help folks get their problem resolved.

 

Yes, Thanks 4.2Paul for this info. I replaced my intake gaskets in my 3.8 trying to fix the dreaded P0171/P0174 codes and that wasn't the answer. It was the bolts with rubber grommets that hold the lower plenum down.They shrink or get hard over time ,leading to vacuum leaks. Thanks again for the good info.....

 

My 2004 F150 would get that code when I first start the engine. I replaced all my oxygen sensors, pcv valve, gas cap, and cleaned the maf sensor and still kept getting the code. Never had any driveability problems, the truck run great. I recently had it smogged and it pass smog with flying colors. The emissions readings are better than average. So I said forget it, as long as it drives good and pass smog I wont worry about it.

A co-worker told me to try Chevron fuel with Techron and I did. So far the code have not returned. Before using the Chevron fuel, sometimes after I start the engine and check my code reader, the code would be triggered in my code reader but not trigger my service engine soon light. After using the Chevron fuel I notice that the code is not being triggered in my code reader at all. That's a good sign - so far, so good.