p0171 trouble code

[mikeg216]

Hello all,
I have just inherited my ex girlfriends 1998 ford explorer sport 4x4 sohc with a 5r55e transmission. It was barley running when i got it it was misfiring and idiling rough among other problems. I did a full tune up changed all the fluids,oils gaskets,filters and all o2 sensors.Now before i did the tune up i was getting a steady 20 mpg.



Now that i did the tune up i am getting 8 mpg its running sluggish idles rough on start up in the morning till it warms up. I am getting the p0171trouble code. Which is bank one sensor one running too lean or rich. And now i tried to pass emissions testing emissions testing this morning and now its failling because the level of carbon monoxide is waaaay too high.Where as before the tune up it would pass no problem.What should i start doing to fix this problem?
Thanks,
Mike G

 

[drdoom]

Check for vacuum leaks (hoses, intake manifold gaskets) and if that does not help check the MAF.
A story: I was doing some work on my SOHC, then when I finished P0171 & p0174. I had inadvertently knocked a hose loose at the IAC.

 

[mikeg216]

Check for vacuum leaks (hoses, intake manifold gaskets) and if that does not help check the MAF.
A story: I was doing some work on my SOHC, then when I finished P0171 & p0174. I had inadvertently knocked a hose loose at the IAC.

i will check it out, i did just clean the MAF sensor maybe i knocked sumpin loose