I have a 1998 expedition 5.4L. It has cold air intake, cat back system, JBL shorty headers. I was trying to help my gas milage (9-10mph-town). I removed the cats and added rear o2 simulators. The truck did fine until I installed my 87oct superchips program. I then got P0155,p0135,p0171 codes. I then replaced both before cat o2 sensors. Same codes. I cleaned the MAF and checked for intake and hose leaks. I replaced pvc valve but found no leaks. I then installed high flow cats and removed o2 stimulators. I still got p0155,p0135,p0171 codes. i then tried a second new before cat o2 sensor. So I am back where I started from. New cats,new sensors,stock programing. I still get the same 3 codes. I also noticed that the truck idles a little rough when cold but smooths out a little when hot. Idle seems about right, not too high or too low. Also power is down and the truck does not run as well as it did before I started all this mess. The dealer also checked the wiring to the o2's-ok. Now the dealer wants to replace the intake manifold gaskets ($450). I am trying to eliminate everything before I do this. Can anybody help!!!!!!!!!! Thanks Fred

 

hi Fred, welcome to the forums...

i did a search for these codes (you should ALWAYS search for keywords in your question before posting a question - just a heads up) and have found that MANY people are getting these same 2 - 4 codes...

p0155
p0141
p0171
p0135

...they are showing up in varying combinations with a few others from time to time but the ones you have are common trouble codes that seem to show up at the same time.

i am yet to find a thread that successfully troubleshot these codes but will lyk if i come across an answer.

 

hey, i almost forgot. i know you checked the pvc valve but did you check the rubber boot that connects up near the throttle body?

you may be having this problem that's sometimes related to the p0171 code and it may be the cause of one or two of the other codes as well...

http://www.azda.com/ford/

...you have a 5.4L engine too so i would definitely check your vacuum line that's connects PVC and intake.

please post back to let us know if this helps.

 

Remove the Superchips module, reset everything to factory, and start over.

Steve

 

I already returned the truck to stock condition and checked all lines for leaks. I also replaced the pvc valve. What realy stumps me is that I am getting a lean code for one bank only (p0171) not the other bank (p0174). If I had an intake manifold leak I would get a lean code for both banks? I am still checking the forums for possible answers with no luck. Thanks everybody for your replys!

 

You can get a lean code on one bank due to an intake manifold leak. It is possible to get a leak to only one of the intake runners, thus causing a lean on one bank (side) only.

 

It sounds like I am going to be putting intake manifold gaskets on this week. I just hope i can talk the dealership into charging me less than the $400 price I was quoted. Thanks again!

 

I had the intake manifold gasket replaced ( bad shape) and the too lean code cleared up. But now I can't get rid of the p0135 and p0155 codes. I have replaced everything ( ford front o2's, Bosch rear o2's, cats, muffler, PCM, pvc valve and hose). All sensor and PCM wires have been checked and we can not find any vacum leaks either. The dealer wants to replace the Bosch o2's with ford ones. Other than that ??????????? Any Ideas? Thanks!