94 4.0 Ranger OBD-I code 172

[DavidTC3]

I recently got my engine replaced in my ranger. After I got it back the check engine light came on. It would come on and go off. I got it scanned by the guy that replaced the engine and he said it was the o2 sensors. I replaced both of them and it still came on. Only now it stays on instead of going off. I bought a thirty dollar OBD-I scanner and scanned it myself. It's pulling 172 which is a lean code. I checked for vacuum leaks but not very thoroughly. I haven't really checked for exhaust leaks or anything else. I've read that it could be something to do with fuel pressure or airflow. Ive put a good bit of money into this and that on the truck in the last month and I'm tired of throwing parts at it. I've got a thirty day warranty on the motor and really want to figure this out and make sure it doesn't have to do with the engine itself. Also it hasn't been getting the mileage that it was getting before I had the engine swapped. I only know of two o2 sensors and I'm not sure if they're different from one another cause they're both upstream of the catalytic converter. I have two weeks left on the warranty... So yeah. Thanks in advance for any help and advice.

 

[1994Ranger$$$pit]

I believe there is 3- O2 sensors.
Two before the CAT and one after.
It could be the post CAT sensor.

But,I'm not sure if that would throw a 172 code.
We I had an intermittent CEL like that it was a a lose O2 sensor.
That caused a exhaust leak right at the sensor.

 

[DavidTC3]

I believe there is 3- O2 sensors.
Two before the CAT and one after.
It could be the post CAT sensor.

But,I'm not sure if that would throw a 172 code.
We I had an intermittent CEL like that it was a a lose O2 sensor.
That caused a exhaust leak right at the sensor.

I was told that it only had two o2 sensors so that's all I looked for at the time. I'll look again later on when I get home and post back again thanks!