Got to say, I do love my truck, and my Expedition, but man oh man......the OBD codes are driving me nuts. Maybe its my lack of experience with them, but you think you fix one and up pop two more, and then the old one comes back............. ok, enough venting......


right now I am working on the 97 Expedition, 5.4. It has been idling really rough. Every once in a while it kinda stalls out, but just for a second or two, and not that often. I was getting a ton of codes,0136 0156 0171 0174 1131 1151. The Autozone guy says its the o2 sensors, so I replaced all four and cleaned the MAF. The good news is I am down to 4 codes, 0136, 0156, 1131 and 1151. 0136 and 0156 are o2 sensors again, and 1131 and 1151 are fuel air mix/management. I have also recently (15k ago)changed out the plugs. Now I am at a loss. I am going to chase around and see if I can find a vacuum leak but not really sure what else to do.
You know, this adventure in codes is kinda like some deranged mystery, find a clue....follow it.....find another clue.....follow it.... and so on and so on

Any words of wisdom would be appreciated.

Thanks
ordkhntr (short for Oregon duck hunter)

 

you probably needed the 02's anyway but not to get rid of those codes. i think you have a vacuum leak maybe. Check the pvc elbow at the back of the intake behind the throttle body. The front 02 were the only ones you needed to replace the rears only verify the cats aare working so that was a waste of money. You might need an IAC but start off looking for vacuum leaks. Clean you MAF sensor to.

 

I am not trying to be an insult but you have to begin to know there is more to this than just code numbers.
136/156 are the same discription for a down stream sensor wiring issue, not the sensors themselves.
1131/1151 are indicating the same sensor has an issue. the PCM cannot detect the switching that must go on under normal operation. Is it the wiring harrness as the 136/156 codes are complaining about?
So you see the problem is narrowed down to an issue with one sensor "operation", not a whole bunch of different problems.
You have to look these up and begin to see the pattern.
After these are cleared, then you may see others that are being covered up.
In the case of the 136/156 lean codes, it is because the PCM cannot correct for an over rich fueling issue that 'may' be caused by an intake air leak.
Since the Ox sensors were worked on look at the harness for being burnt against the exhaust.
What people don't understand is the codes are the only way the system has of alearting you to an issue that may be far removed from the 'end result' the code discription gives.
Example: a code that says 'lean'. It doen not mean the motor is running lean but that the PCM fuel tables are at their lean end point in trying to correct a RICH condition. This is all only in software fuel tables and not that the motor is actually running lean.
You have new ground to break in understanding what is going on or you will be at this forever.
Good luck.

 

no insult taken, I appreciate all the help I can get...and lord knows I need it!

I will be the first to admit that I am no expert, and that I am just beginning to learn this stuff.

I see where what you are saying makes sense. I tried asking if the lean code was because it just couldnt correct enough and I got this glazed look. I checked the wires from the downstream O2 sensors as far as I could, but I am going to crawl back under there and do some real looking to see where they connect up with the harness and then try and follow the harness. I will also take a look up around the EGR and such for a vacuum leak. I listened real quick last night and thought I could hear a hiss up around where the EGR is. Should there be a hiss noise from up there??

Thanks again

 

How hard is it to unbold the egr and clean out the carbon build up, if there is any? im getting the same codes but i think it's because i have a broken bold on my exhaust manifold.