2000 came with a 2.5l, got swapped at some point to a 3.0 no cats on it. Going to redo exhaust and I need to know how many cats should be on it. I'm going to use the jba shorty headers and a flowmaster 40 series 2.5 in dual 2.5 out. I've seen cats on ebay that have the 2 cats on the y pipe, but my question is about the rear cats. I see 2 rear cats with the o2 sensor in before both cats and I've seen it with the 02 sensor between both rear cats. Other question @RonD since I'm sure you're gonna end up reading this lol, if I didn't go with cats, how much will that mess with fuel milage and how well the engine runs? The current front o2 sensors are hooked up, but it's running like poop. Way to rich. So I'm going to replace the maf, iacv, and all 3 o2 sensors. Getting them from ebay, since I've never had issues with parts before. Also is there anything else emissions or fuel related I should replace? Already did fuel filter. I'm running auto-lite platinum plugs.

 

You would need to look at what the O2 sensors are telling computer after engine warms up to see why its running too Rich
O2s need their heaters to work
O2s generate their own voltage, 0.1v to 0.9v, once above 650degF
0.1v is High Oxygen, we call it Lean
0.9l is Low Oxygen, we call it Rich

O2s can't "see" fuel so it not really Lean or Rich, lol

When O2s get older, 12 years or 100k miles, they run out of the chemical that creates the voltage, so voltage drops and computer see high oxygen so adds more fuel that is un-needed

If exhaust manifold has a leak then AIR is sucked in, more Oxygen, so O2 shows lower voltage a computer adds more fuel thats un-needed
Any OBD2 reader can show you O2 voltages in real time



Cats work best the closer to the engine they are, they need to be HOT to work, this is why you will often see smaller Cats on the Y-pipes of V6 or V8 engines, but still at least 1 Cat after the Y-pipe
But you can use one larger Cat or 2 smaller Cats in-line after the Y-pipe, then the rear O2 sensor
Rear O2s should show 0.75v to 0.85v low oxygen because Cats burn up the oxygen as they burn up pollutants
Yes, without the Cats and rear O2 sensor the computer will throw in extra fuel now and then to try to get the rear O2 sensor voltage up higher
Cats also use unburn fuel to stay HOT, if rear O2 sensor is not working or its showing high oxygen then computer tries to "make it work"

 

hey rond, thanks for the reply. i know i have an exhaust leak from the ***** weld job they did. hence why im just going to redo it all. im planning on replacing the maf, o2 sensors, cats, headers with jba. let me know if the following items will do.


o2 sensors

upstream cats

headers

maf

downstream cats

 

Never used any of those but they look like they should be fine

 

I got my cats from ontario exhaust, and the same for a friend of mine. The y pipe cats on mine fit near perfect to the manifolds. and on my friends Ranger we had to slot the bolts holes because mine came slotted, and his came with a single round bolt hole? don't know why but they line up fine to the exhaust system. This is the ones we got for our 2000 Ranger 3.0, 1998-2000 FORD RANGER 3.0L/4.0L/MAZDA B3000/B4000 FRONT CATALYTIC CONVERTER (#184773532054) and 1998-2000 FORD RANGER 3.0L/4.0L/MAZDA B3000/B4000 REAR CATALYTIC CONVERTER (#184773531978). I used Bosh O2 sensors
BOSCH 15719 (Daily Driver) Bosch Engineered Oxygen Sensor Info
Downstream
and
BOSCH 15716 (Daily Driver) Bosch Engineered Oxygen Sensor Info
Fits Upstream Left; GAS
or Upstream; FLEX Fuel.
ours are both both flex fuel 3.0.
But they both had bosch sensors. So maybe they were OEM, But it may of been just a coincidence.
I am not saying this is for your situation. This is just worked for me.

 

@Curt G thanks man that helps me out a lot. I'll be ordering everything pictured above in 2 weeks when taxes get here. Already ordered the maf. Going to get the flowmaster 50 series exhaust cat back system. Yeah almost 800 is a bitch but I have the same exhaust on my power wagon and love it.