1999 mountaineer codes p171 and p174

[mountaineer99]

I have a 1999 mountaineer that codes 171 and 174 keep coming up.
I have replaced the oxygen sensor and I have checked the mass air flow sensor. The intake manifold gaskets have been replaced.
I can not find a vacuum leak.
I think I have a bad fuel injector. Is there a way to test them?

 

[Gabe96Explorer]

Spray Throttle Body Cleaner around the intake area.. hit the EGR uppipe too. That should help you locate your leak.

 

[mr2fix2it]

need more info 4.0 sohc or 5.0

 

[mountaineer99]

99 mountaineer 4.0l sohc p171 and p174

I have the 4.0l v6.
the p171 and p174 codes keep popping up.
I have replaced the intake manifold gaskets and o2 sensors

 

[mr2fix2it]

you gotta have a vacuum leak look at pcv system also look around egr pipe going into intake i have seen the pipe bent and not fitting properly into intake you can check with carb cleaner look for rpm changes