Hello folks, I JUST bought a Ranger used from a friend for just about nothing, but it has a few issues that I want to do myself rather than spending a ton at a shop.
So, let's get right to it: I bought a used pickup, and the check engine light was on. The truck has only 56k miles on it, but it was rebuilt. What I THINK the issue is, is that I need a new Oxygen Sensor, but I want to check with you guys before I purchase anything.
The truck idles a little low, and when we got a code readout, all it said was "running lean". The truck also has no working AC, and the overdrive goes out if I drive the truck too hard. It struggles up steep hills, and the RPM goes up and down about 200-300 rpm when going up hills. It's been eating a lot more gas than it should, and it takes a few seconds to kick into the right gear once it's going. From the research I've done, it sounds like an Oxygen Sensor is out, and throwing the whole computer out in my truck. When I bought the truck, my friend did mention something about the o2 sensor, but he didn't know much about it.
If this sounds like the issue I am having, please let me know what I should do about it. If it's possible to do myself with the right tools, or if I should just take it to a mechanic. I really appreciate any help from you guys, thanks for reading!

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2000 Ford Ranger XLT
4.0cl v6 4x4
Automatic

Invest in a code reader so your not throwing parts at it.It sounds more like a bad vacuum leak to me.

Probably your lower intake bolts are loose that is what gives you the lean condition.

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1999 Ranger 4.0 and extreme Snap-on tool fetish

There are a few things that would give me a "lean" readout. I took it to NAPA and used their code reader, all it said was "running lean"...no codes.

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2000 Ford Ranger XLT
4.0cl v6 4x4
Automatic

Running lean means you got codes p0171 & p0174. Did you? Or not? How exactly did Napa pull that "diagnosis" out of nowhere?
Those two codes signify trouble with extra air sneaking into your engine somehow.

The usual suspects are vacuum hoses (any 1 or many). Or gas cap is leaking. Or PVC elbow is cracked. Or MAF sensor is dirty. Or IAC is dirty. Or intake manifold gasket is leaking. Or fuel rail gasket is leaking. It's VERY seldom caused by a bad O2 sensor, but yeah, it's possible.

Get a code reader: search Amazon for "ELM327", which talks to the freebie "Torque" app on your smartphone. It'll come in handy many times.

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1997 4x4 Mazda B4000 SE, Ext.Cab

Thanks a ton man, i will do a smoke test today with it to find the Vacuum leak.

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2000 Ford Ranger XLT
4.0cl v6 4x4
Automatic