So I got my truck a few days ago it’s a 2000 ford ranger 3.0 4x4. And it had a check engine for misfire on cylinder 6 and o2 sensor because a cat was cutoff. I put o2 spacers and welded it back on. Changed all plugs and wires. No more misfire codes. But now I have a code for system to lean p0174 bank 2. I need to get check engine gone for emissions or else I can’t register it. Anyone got any ideas? It does have 246k miles. Some cats are hollow because they were clogged. Could it be injectors? Maf sensor? Clogged cats? O2 sensor?

 

O2 sensors need to be changed every 12 years or 100k miles
They use a chemical reaction to detect Oxygen in the exhaust and they simply run out of chemiicals
Like brakes, tires and batteries they just wear out over time

And when they are running out they set Lean codes

Ifs a V6 engine so if there was a fuel issue you would get BOTH sides with lean codes
P0171 System too Lean (Bank 1)
P0174 System too Lean (Bank 2)

So if you haven't changed both these upstream O2s then do so, 2000 Ranger V6 should just be getting its 3rd set of O2's at 23 years old

If P0174 comes back then it could be an exhaust leak on Drivers side exhaust manifold or lower intake vacuum leak on that side
But if its an O2 sensor issue then you are just chasing ghosts, no leaks a reporting error

 

thank you. I’ll try that. But I’m confused on why the code never popped up before until now. All of a sudden o2 sensor? But they look like original o2 sensors. I should probably go ahead and replace them.

 

Things work until they don't

In the case of O2s they slowly go bad, until they reach a point that sets a Lean code, and since there is just the one Lean code it can't be things that are common to both banks of a V6 engine, like MAF sensor, upper intake vacuum leak or fuel pressure

If the O2 sensors were newer then you would check other things common to just that one bank of the engine
But if you don't know the age then the code may be in error, because of that sensor
Once new sensors are in then that code could mean something else, and your MPG will go up for sure, at least for the next 12 years

 

I took out an o2 spacer because there was two and now it doesn’t have the lean code anymore. And I drove it around no codes. After 20 miles of driving the same misfire code that I bought the truck with came back. It’s misfire on cylinder 6. But there’s no vibrations or any noises or sounds or anything that would show misfiring. Truck runs great. I changed all spark plugs and wires but I don’t know why it’s back. Could it be injectors? It does have almost 250k miles. I did put some Lucas fuel treatment in the tank but I don’t think it’s gonna do much.

 

No sure what an O2 spacer is but OK

Does the CEL(check engine light) flash or do you just get P0306 code and CEL comes on steady?

Flashing CEL means hard misfire NOW, back off the throttle
No flashing CEL but P0306 means power imbalance when #6 is suppose to be adding power to the crank
Crank and cam sensors with computer have millisecond timing so can see minute changes in rotation of crank and cam, but if you don't feel it it can be an error

Anytime there is a misfire you do a compression test on all 6 cylinders, to take burnt valves off the table
Messing with spark and fuel may be easier but can just be a waste of time and money if its a compression issue

Pull spark plugs 5 and 6 and compare the tips
If 6 is a slightly different color then there is an actual problem in 6, its color can tell you where to go next

 

The o2 spacer is for the o2 sensor to not throw a check engine because of the cats. They are hollowed. The check engine light only comes on and stays on after 20 miles of driving. No flashing. I’ll try a compression test but when I was changing out the plugs all of them plugs looked identical pretty much. None were discolored more than the other or anything.