msteele516

Just a quick posting to thank the F150 forum for being there. After experiencing the above "System too Lean" codes and "EGR flow insufficient" I read nearly every entry on solving this problem for my 2002 F150 4.2L. This truck has 252,000 miles on the odo, and still gets 19MPG, but when pulling a trailer I would hear a light pinging indicating pre-ignition. Since this is sometimes caused by a lean mixture condition, I decided to fix the problem before I did some serious damage. Pulling and cleaning the EGR and it's attached tubes; cleaning the MAF sensor and trying an assortment of fuel additives did not help. Finally, I pulled the top of the intake plenum and cleaned each of the 6 orifices underneath. The only replacement I performed was the DPFE sensor. Ford wanted $89. I found one produced by airtex (5s2047) for $27 which worked perfectly. No more trouble codes!! Feel free to contact me on pulling the plenum....it's a 10 minute job that takes about 2 hours. Regards to all.

NGM

a 10 minute job that takes 2 hours? lol

dewman

sounds about right...

Magas

Hey ;
I do need your help. I have error P0171 - take a look at my post here :
https://www.f150forum.com/showthread...ighlight=p0171

Now I was just going through other guys struggled with this error and yours seems to be more realistic. please let me know where to start from and how to do it .
thanks

msteele516

Well the fix is not going to be easy. I jokingly referred to it as a 10 min job that takes 2 hours. It will take every bit of that! Take a vacuum reading at the plenum and see if it is less than about 20 in/hg. If so, you probably have a gasket leak underneath the plenum. Start with a cool engine cause you will brand yourself if not. Label and Remove air intake snorkle, and all plug-ins to plenum. Remove throttle linkage. Release spark plug wire keepers at each corner of the plenum near the firewall. (They pull straight up off the post once released.) There is a sound-deadening pad that is between the plenum and the firewall. Cut slits at the narrow points on both sides and remove (you can spend an extra 2 hours and remove the fasteners if you have gobs of time.) Now you can get your hand/tools to the back side of the plenum to remove the 10mm bolts that retain the clamshell top. Remove the top of the plenum. Inside is a series of baffles. Remove the screws retaining the baffle plate. Underneath that plate are 6 brass-appearing orrifices. These will all be clogged from EGR gasess. Clean them. You may have just fixed the problem at this point as that took care of my trouble code, however since you are this far along, and if you had a low vacuum reading, you might as well replace the intake manifold gasket underneath the lower clamshell part of the plenum. Most are factory-cracked. Saves time cracking them in the field! Replace this gasket and re-install. Good Luck. Let me know if this helped.

Magas

thanks for the reply/
any pictures ? dont get mad , am just asking ...

so , It's not mandatory to change the gasket if you open the plenum ? I was just checking on A-zone . they have it for $45 for my truck and I dont wish to pay for thay ...

msteele516

Sorry. No Pics, but the memories will last a lifetime!

What will mandate a change-out of the gasket(s) or o-rings will be whether or not it is sealing the two surfaces it separates. In the past I have used (O2 sensor friendly) Blue RTV with great success. $4 a tube and maybe save the $45. Problem here is that a visual inspection may not reveal a seal failure as previous posters have noted a change in the compostion of the grommets and o-rings. There could be a temperature-sensitive compression failure of the rubber (remember Morton-Thiokol's SRB o-ring failure?) I believe I would decide if I wanted to risk saving the money upfront by using a sealant with the possibility of re-doing the entire job and having to pay for the gasket kit anyway.

By the way, If anyone would ever get mad by sharing their knowledge with another, they need to stay away from forums such as this. Glad to help.

jyokos

I found a Ford TSB on this problem (TSB 05-16-5.) It states all the repair as stated above. I've got the same problem. Only thing is that Ford recommends changing the isolator bolts that have a "black" sealant to a "green" one. It seems that exhaust gases are leaking through the isolation bolts between the upper and lower manifolds.
My question is "was it necessary to replace the DPFE sensor?" is this something that might help in the future? Another thing is if this is a Emissions problem will Ford do the work under the emissions warrenty coverage? Thanks for sharing.

Good old Bill

jyokos, I replace the bolts w/seals and O rings on my 02 4.2L. Yes it did fix the problem for codes P0171 &P0174. The DPFE, I bleieve the original thread starter replace it to correct the P0401 code.

jyokos

Just wanted to leave some feed back on PO171 & PO174. I did the job in about 3 hrs. The throttle plates had a lot of varnish and carbon on them.
I would like to suggest:
8 (ea) "green" isolator bolts. Get them at FORD parts dept.
they can print you a IPB for referance
4 (ea) upper intake manifold seals, looks like figure 8's
a couple of cans of carb cleaner.
*optional upper plenum seal.
The isolator bolts seals had become "hard" and the upper intake manifold seals had allowed bypassing between chambers. to remove the isolator bolts flip the intake manifold over and use a 3/8" deep 1/4" drive socket to remove the isolator bolts. Tap them out gently. Once cleaned and reinstalled the codes haven't returned. I changed the plenem seal since I had everything opened up. Don't forget to torque the intake/plenum to manufactories spec's. Good luck