Hi guys this is my first post. I have a 2002 Ford ranger with the 2.3l and a five speed. It has 205000 and I have owned the truck since new. When I put gas I always fill the truck up completely and reset the trip so I can see how may miles per tank it gets. I use 87 octane and from top tier stations. I change the fuel filter about every 15k-20k. I just did the plugs for the second time in the live of the truck. The old plugs were pretty clean no sign of burning oil and the truck has never smoked. I've noticed that it's been down on power and the mileage is about 50mi per tank down. One of my suspicions is maybe the catalytic converter needs to be replaced but I'm really not sure. Any help would be appreciated!

Thanks
Karl

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2002 2.3l 2WD

Feel the passenger side floor and if hot, the cat converter is clogged. Spray off the MAF sensor.
If these two check out then pull the codes at an auto parts store.

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Have you ever replaced the upstream o2 sensor? Do you have access to a scanner with live data so you can read the fuel trims? Do you have a vacuum guage? Very easy to test clogged cat with a vac gauge.

No never replaced the 02 sensor. I do have a scanner and a vac gauge.
Also there is no check engine light on.

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Unfortunately there is no check engine light on. If it threw a code that would be on correct? I know with my mustang that is the case.

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2002 2.3l 2WD

Hook your vacuum guage up to the intake somewhere and then hold the throttle steady around 2000 rpm. If the guages holds steady your cat is not clogged, if it slowly drops in pressure you have an exhaust restriction in the cat or muffler.

O2 sensors are good for 100-150k miles so yours may be failing and causing it to run rich but not enough to set off a code yet. (Also verify your check engine light works, it should come on momentarily when you turn on the ignition).

If you can use your scanner to view live data there is alot of usefull info there. Your long and short term fuel trims will tell you how much the computer is compensating either adding or reducing fuel injector pulse width. If your fuel economy is crap then you most likely have a positive fuel trim. But it again could be just under the threshold to throw a lean code.

Like dvrich mentioned also check your MAF sensor and clean it.

That sound good I will try it this afternoon. Thanks for the info and ideas!

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2002 2.3l 2WD

With no code presented, I would be looking at the O2 sensors(upstream) as the guys mentioned. They can become a little slow to respond to changes in the exhaust gas makeup, so the computer is a little more 'sloppy' in adjusting the spritz time for the injectors. A MAF will generally give a 'response' indication when it is a little off, causing hesitation on acceleration that may be more noticeable. If the fuel pressure were a bit high, and not able to be regulated to the desires pressure, the injectors would flow more than the computer wanted. I figure the trims would be negative for that...
tom

What about the clutch? Sounds crazy but my 2002 5spd gained about 50mi per tank after I dropped a new clutch in. What RPM are you at if your going 70mph?


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4-cylinder squealin tires like a bag o' pigs! Yeeehaww

I ordered a Motorcraft upstream from Rock Auto last week so hopefully I'll be able to install it this week end. It still has the original one so it cant hurt to change it out.

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Funny you say that, I'm still on the original clutch. I was thinking that it was possibly slipping causing the issue but I had a Mitsubishi Mighty Max that the clutch went out and you could tell when it started to go. With the Ranger it still feels like it's grabbing good.

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2002 2.3l 2WD

That is what was weird about mine is it felt fine and even the mechanic said it was fine. But my brother who is a crazy Millwright took it for a spin on the freeway and insisted I put a new clutch in at 100k and I got better mileage. So yeah, kinda out there but thought I’d throw my experience out there.




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4-cylinder squealin tires like a bag o' pigs! Yeeehaww

The only test for a clutch (other than it smoking, and no movement...) was to get into top gear(not OD), and floor it. If the rpms went up faster than vehicle acceleration, there was slippage.
I have a set in the basement, and just received a new flywheel, so I am ready. Right now, the pedal comes up pretty high before there is good engagement. I can(though I do not) just push the clutch pedal down a couple inches to shift. I be thinkin' its pretty wore out.
There is no adjustment on my original, and the replacement does not have the ramped sliding mechanism so it also will (I think) act the same way as it wears.

I replaced the O2 sensor and mpg seems to have increased. It also feels as if the engine is running very well, better than it has in a long time. I got no code, but it was on sale at Rock, so I figured it was time.
As the O2 ages, it will tend to produce less signal, which is a tendency to report 'lean' conditions more, leading the computer to add fuel attempting to bump up the sensor output. I dunno if the computer learns that its O2 sensor is getting lame, as in always a bit lean, by monitoring the 'rich' condition it could create by pumping in more fuel and looking to see if the O2 responds. It could 'know' its O2 was not responding and reduce its attempt to correct for lean accordingly. Does it do that? I doubt it.
tom

The computer uses the upstream o2 sensor to set the short term fuel trim, it cant "learn" to compensate for a faulty reading because it has no way to tell if the reading is faulty. Even if it tried to pulse more fuel as a "test" it has no idea how much fuel came from the pulse without the o2 telling it that the wider pulse actually resulted in more fuel. The injectors themselves have no sensors. Imagine this scenario, the computer sees the o2 sensor reading lean and says screw you thats BS and stops adding extra fuel to compensate. The problem was actually related to fuel pressure or clogged injectors not the o2 sensor giving faulty readings.... Your engine is now running dangerously lean because the computer ignored the o2 sensor.

Now the computer can detect if the o2 sensor is malfunctioning when it fails under certain criteria ( then you get a cel and a code ). An o2 sensor can degrade and send bad readings long before it ever meets the criteria for the computer to throw a code.

When the o2 sensor does fail in a way the computer can detect it still does not exactly compensate. It will "usually" result in the computer putting the system in "open loop" mode. Open loop is essentially a factory programmed tune. It takes the sensors out of the equation and runs strictly on what the programming tells it. Open loop is usually really rich and inefficient because its main purpose is for startup while the engine warms up.

I have the new o2 sensor I just need to install it. Hopefully this weekend I'll have time. On Rock Auto the Motorcraft o2 was half the price compared to autozone or o'riley. I'm sure it is worth doing seeing the stock one has over 200k miles on it.

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2002 2.3l 2WD

Yes! O2 sensors have a chemical lifespan, not mechanical. At 200k it is a dying or dead o2 sensor no matter what.