Ford Enthusiast Unofficial Resource

Go Back   Ford Forum - Enthusiast Forums for Ford Owners > Ford Trucks, Ford Vans & Ford SUV's > Ford F-150
Sign in using an external account
Register Forgot Password?
Search


Welcome to Ford Forum!
Welcome to Ford Forum,

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!


Reply
 
 
 
 
LinkBack Thread Tools Search this Thread
  #1  
Old 03-09-2009, 12:47 PM
Junior Member
 
Join Date: Mar 2009
Posts: 3
Default Ford Code P0171 and P0174

Just bought 2004 F150 Lariet 5.4 pulled codes p0171 and P0174 Ford store says I need to replace all 4 cats Hard to believe all 4 went out at the same time. Any thoughts on this THX truck has 82000 miles on it

Last edited by diehardgator1; 03-09-2009 at 01:00 PM. Reason: add to
Reply With Quote
  #2  
Old 03-10-2009, 06:15 PM
Senior Member
 
Join Date: Jan 2006
Location:
Posts: 1,234
Default

First thing to do is look for a vacuum leak that may affect both banks of the engine. Also low fuel pressure or a mis reading from the MAF can give those codes. If you do not have an emission inspection soon, erase the codes and see how long it takes to return.
__________________
People are like Slinkies. Not much use, but it still makes me smile whenever I see one tumble down the stairs.
Reply With Quote
  #3  
Old 03-10-2009, 07:41 PM
Member
 
Join Date: Mar 2009
Location: Millis, MA. (Originally from Maine)
Posts: 63
Default

Its not your cats...
It is most likely that the MAF sensor is dirty. If you have an oiled air filter (K&N) and over oiled it it would cause the MAF to get dirty. In most cases like this just cleaning the MAF will fix the problem. Clean it with brake cleaner, or electronics cleaner if you have any. Make sure that it is COMPLETLY dry before you reinstall it.
So... check the MAF, the air filter, and make sure that there isnt a vacuum leak before the MAF also. it might also help to check your fuel pump and filter, and possibly injectors too if that doesnt work. It is reading to much air, and not enough fuel so its either one or the other or both! I hope that helps. at least it will be cheaper than all four cats.
Reply With Quote
  #4  
Old 03-11-2009, 01:13 PM
Junior Member
 
Join Date: Mar 2009
Posts: 3
Default

Put a new maf sensor on the light came back in about an hour. The dealer did not charge me for it so lucked out there. I have a ford mech of 20 years working on it after hours he hooked a computer up and we drove it while hooked up The fuel pump was good the filters clean. Seems like when you first start truck it idles good but the longer it runs the worse it gets and then will shut off. Will crank right back up Before it shuts off it starts to stumble or run rough and then wam off she shuts off He said the injectors were checking good also
Reply With Quote
  #5  
Old 03-11-2009, 02:24 PM
Member
 
Join Date: Mar 2009
Location: Millis, MA. (Originally from Maine)
Posts: 63
Default

Check if the EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor [COLOR=blue ! important][COLOR=blue ! important][COLOR=blue ! important][/COLOR][/COLOR][/COLOR]that monitors EGR flow is faulty and is under-reporting EGR flow). could also cause the Ho2 sensors to tell the PCM that it is running to rich, or to lean. It is fairly common when this happens to trucks (over 60,000 miles), and it is usually the DPFE (Differential Pressure Feedback EGR) malfuctioning and sending to much, or not enough exaust back into the intake. Try this, and see if it fixes it. I will try to find out more if it does not. Goodluck!
Reply With Quote
  #6  
Old 03-11-2009, 03:17 PM
Junior Member
 
Join Date: Mar 2009
Posts: 3
Default

Just talked to the local Ford store they say this truck has no EGR or DPFE valve
Reply With Quote
  #7  
Old 03-11-2009, 03:45 PM
Junior Member
 
Join Date: Mar 2009
Location: springfield il
Posts: 2
Default

dont know how cold it is were your at ,but the upper intake gaskets have a tendency to shrink when real cold ,this is when they leak as engine warns they seal , this throws the fuel trims out of wack long enough for pcm to try and make correction, also hope your not running e85 this also causes lean concern, you said you replaced maf, just make sure there are no vaccum leaks for pcv ,air cleaner lid is succure,all clamps fitting the air snorkle tube are tight for unmetered air
Reply With Quote
  #8  
Old 03-11-2009, 08:53 PM
Member
 
Join Date: Mar 2009
Location: Millis, MA. (Originally from Maine)
Posts: 63
Default

That makes sence. Ide deffinatly check the gasket, and make sure that you dont have any vacuum leaks ANYWHERE before the MAF that might cause the PCM to over compensate.
Reply With Quote
  #9  
Old 03-18-2009, 01:38 PM
Senior Member
 
Join Date: Nov 2007
Location:
Posts: 379
Default

Does your friend have a scanner that can read snapshot information? You need to know the conditions present when the codes are set. If it is when the engine is warming up, you may have a problem with the intake gaskets. I would look at the pcv hose where it attaches to the back of the intake manifold. There is a rubber elbow there that deteriorates with time and gets a small pinhole in it. I sell a number of these.
And no on the cats, they will not set a lean code. Can't even believe the dealer told you that. Doubt if I'd go back to them for anything.
__________________
Too Old to Work, Too Young to Die.......GO fishin'
35 Years with Ford
ASE Master
Ford Engine Master
L1

Last edited by oldtimer35; 03-18-2009 at 01:42 PM.
Reply With Quote
  #10  
Old 08-19-2013, 11:43 AM
Junior Member
 
Join Date: Aug 2013
Posts: 1
Default

This is why these forums are valuable. Had the 0171 - 0174 codes come up on my '04 v6. Mech #1 says replace intake manifold and all vac hoses - $650. I says go pound salt. Mech #2 says it's your mass airflow sensor - $110. I looked on an online forum and learned it's most likely a vacuum leak. You can do a smoke test for $75. Or...

So I took a good look and eureka - the boot connecting pcv valve to manifold has a rip. Repair cost - $2.50. Runs like a champ.
Reply With Quote
Old 08-19-2013, 11:43 AM
 
 
 
Reply

Tags
codes, correcting, dpfe, e150, econoline, expedition, explorer, fix, focus, ford, freestar, fusion, kn, p0171, p0171p0174, p0174, pcm, sensor

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Advertising
Our Sponsors
Vendor Directory
New Sponsors
All times are GMT -5. The time now is 09:20 AM.

© Internet Brands, Inc.


This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford® is a registered trademark of the Ford Motor Company.

SEO by vBSEO ©2010, Crawlability, Inc.