NAU Ranger

so i bought a 97 V6 4.0L ranger xlt truck off a friend and iy idles higher than normal about 1100. the engine light recently came on. i had a diagnostic ran at autozone to figure out y this is happening and the codes were P0171 and P0174. ive replaced both O2 sensors already and only made small difference (idles about 1000) the engine light is still on. anyone have any ideas on wat to replace next? im guessing MAF sensor any ifo would b greatly appriciated

92rangerstx

First off, how does it idle, other than too high, does it fluctuate, does it idle a bit rough? Because if it is, it may be something simple. I only ask this as it can also cause the idle when warm to be a bit high.

I have the 92 version of that 4.0L V6 w/ 218K+ miles on the clock and for a good chunk of last year it'd do just that, fluctuate when cold, dropping to about 100RPMs, sometimes dying and rise up to about 1100RPM's and once warm it tended to stay at about 1000-1100 RPMs, unless I have on lights etc, then the idle would drop to where it should, around 800 or so RPM's.

I only knew that when I had the truck tested for exhaust emissions (yes, it passed, go figure) and in January when I had the slave clutch cylinder replaced, they noticed a whistling noise and discovered a vacuum leak. Plugged it up and now it idles just fine.

NAU Ranger

its idles somewhat rough but it never gets down near 100 rpms, about 600 or 700 at the least.