I have a 1998 expedition, v8 5.4L. i have trouble codes P0136, P0156, P1131, P1151, P0171, P0174. I changed all 4 oxygen sensors and it still runs really rough. i was told to change the mass air flow sensor. i'm really a novice and it took me all day to change the oxygen sensors with the help of my wife who has skinny hands. any input or suggestions would be appreciated.

 

First of all oxygen senors CAN NOT make an engine run bad. Its not possible, but im not sayin yo wasted your money by replacing the sensors. With the codes u have, ur vehicle is telling me that your o2s are not switching properly, upstream and downstream and banks 1 and 2. U are also running lean on both banks. The tricky part is figurin out y ur o2's are not switching correctly. U could have catalst issues, fuel issues and air issues. Its hard to determine whats happening without seeing what the o2s are actually doing.
U r correct the mass air flow sensor can cause some of these issues. The sensing elements are so small and sensitive i have seen a bug wing or leg make an engine run awful. U can remove the sensor and inspect it closely see if u can see anything. I would recomend using MAF cleaner to clean the sensor. Due not use brake parts cleaner it can damage the sensing elements in the sensor. U can also use some air duster, u know the compressed air made for keyboards, works really good. U do not want to use shop air unless it is regulated really low, this can also damage the sensing elements. U may also want to check for vacuum leaks. Check around your PCV hoses, and any rubber vacuum hose. I would also recommend checking your fuel press... I hope some of this information helps and good luck...

 

i removed the MAF sensor and sprayed it generously with MAF cleaner and then used compressed air to try and clean it. hopefully i didn't damage it because i used shop air (did all this b4 reading your post). i did notice some trash (maybe a bug wing) stuck to it and it wouldnt come off. so i carefully removed it with my finger nail. again hope i didn't damage it more (remember i'm a novice). no change in how it's running. I appreciate your advice. i think i'm gonna change the sensor and see what happens. got a friend that has connections at a parts store to let me try and see what happens and then bring it back if it doesn't fix the problem. after that it may roll down a cliff unmanned. only problem is there aren't many cliffs in south louisiana. LOL thanks again

 

I can't believe you wasted all of that money and time on this. Your problem is nothing more than a large vacuum leak at the intake manifold. So either the intake gasket has a problem or the PCV elbow at the rear of the intake is split open.

 

well, einstein, maybe i'm not as smart or have as much experience as you. fyi it was the pcv hose that split at the rear of the intake.

 

That's why you ask questions BEFORE going in and swapping parts. We're all here to try and help people, not make things worse. (Well, we at least try hard to help.) It's frustrating to have someone come to us having already having wasted time, money, and then hoping we can lift them out of the hole they dug for themselves.

 

believe you me i would've asked first if i knew about the website before i started the process but i didn't. bottom line is i wasted the time and money but the website genuinely helped me fix the problem, and i did learn a valuable lesson for the future. not sure why your frustrated, my mistakes are my mistakes no one elses.