question on O2 sensors for you motor heads

One quick note - being a 1994, the truck is NOT OBDII compliant, so gives limited information from the computer.

The sensors do NOT measure resistance, they provide a self generated voltage, like a battery - and virtually all American and all but some Hondas and Toyotas in the Jap world use the same technology. Sensors from a different Ford engine, with the same connectors WILL work, and will not hurt the engine. The 4 wires are signal ground, signal, heater(1) and heater (2). The heater wires go to + and - 12 volt. The sensor ground is grounded at the computer. The sensor signal wire is (generally) fed a 0.45 volt bias signal through a very high resistance. When it gets hot, if lean it goes above .45 (to roughly

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Oxygen sensors are more or less universal. There are three main types though. First (and cheapest) are the 1-wire, which is probably what your truck uses. If you go to an auto parts store and get a Bosch they should be pretty cheap. Pretty much any 1-wire O2 sensor is interchangeable with the major difference between brands and styles being the mounting method. (Some thread in like a sparkplug and some use a two-bolt flange. On the flange type you can sometimes unscrew the sensor from the flange and use it in a non-flange car.)

There are also two, four and five wire sensors. Some of them use a

Also, if your truck has several sensors, usually the one closest to the engine is the only one that the ECM uses for air/fuel delivery feedback. The other one or two are used to monitor catalyst efficiency.

But those "inexpensive" code readers are generally only for OBDII - meaning 1996 and newer.

Had the same problem on my Aerostar (1990) and a new sensor solved the problem.

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Well, generally maybe, but not exclusively. My car has a '93 drive train with a '93 ECU, harnesses and the like. The code reader is designed for a '91 through '93 car and works fine. I was only suggesting he look, not guaranteeing that this would solve his problem.

Peter

Correct, I was brain farting and described a temp sensor :-)

Correct, I was brain farting and described a temp sensor :-)

Gunner wrote in message news:...

Here's what I know from my engine control handbooks. The O2 sensor is an electrochemical cell that generates a voltage that varies depending upon the O2 content of the hot exhaust gasses. It takes awhile to warm up, so most engine controls have a default setting built into the computer until the O2 sensor comes online and starts generating voltage. When new, this is supposed to take 5-10 secs. As the sensor ages, this takes longer and longer. This may be what the "internally heated" thing is about, to cut down on the cold idle time. It used to be that you were supposed to get the sensor changed at about the 50K mile mark or thereabouts, they might have improved things since my last vehicle, though. Lots of stuff can contaminate the sensor cell, lead and silicone along with using the wrong type of anti-sieze. Once they go, there's no fixing them, only replacing them. Without the O2 sensor input, the computer limps along with the default setting, usually way too rich, to avoid burning valves and such. This problem should show up with a computer error code readout. Some chain parts places will do this for free. If the sensor isn't a real oddball, it should be available at the chain parts places for $25 on up. There is no standard on these units, there's 1-wire, 2-wire and, I think, 3-wire. Not like spark plugs, the sensor has to match the computer input. A vehicle might have the same mechanical parts for the engine as another but the computer may be way different. I wouldn't put any faith in a used O2 sensor.

Stan

Trucks are geared differntly, and carry a heavier load. Also note that trucks have a longer exhaust pipe than cars hence the reason they get hotter.

oh, I brain farted on the O2 sensor measuring resistance :-) (I was thinking temp sensor and I'm in the damn business)

Still install the correct O2 sensor.

Keep in mind, they can be a bitch to remove, you may have to heat up the manifold (get it red) before the old sensor will back out. (note* use the correct socket for the O2 sensor, they make one you know)

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Don't necessarily rely upon the 'puter to render any useful info. to a code reader. I've got a code reader and have used it to try and find the error codes on my 89 ranger, and have never been successful in getting an error code that is anything but normal. Maybe the code reader is not capable of reading all the codes the 'puuter puts out???? About all the good I can say the code reader does is keep the "Check Engine" and "Brakes" light off for 15-20 miles, instead of after 2-3 miles. This is only good for the first trip after reading the codes, must do a system reset. So, I'd suggest that if you suspect the 02 sensors are bad, take them to someone who can check it, or do it yourself. One of the other posters suggested a method to test them, sounds pretty easy. I wouldn't change an o2 sensor unless, a) it physically blew up, b) it showed bad on the same tester as compared to the new one that I was going to buy. Don't believe the parts guy who says that you need one just because you got 324k on your rig. I spent $90 on one, "open the box, it's yours" policy on that stuff, just to see if it would cure the problems that I was having. (Pretty expensive lesson on tightening the distributor bolt. DoH!)

Gunner as you know, real pros don't guess :-) Take the damn truck to someone that has a "Snap-on MT-2500 scanner" Have him/her hook the thing up and scan it while test driving. I think that you are going to find a "short" in some wiring harness somewhere (because this sounds an intermitent problem). The "Check engine light" would stay on all the time if the O2 sensor were bad. And you also say that the light comes on while stopping or reducing speed (doesn't sound like a bad O2 sensor to me) At 300,000+ miles these things are going to become more and more common. Leaving you with three choices 1) Be prepared to be nickled and dimed to death. 2) Total rebuild from the ground up. 3) get rid of the thing.

n.

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North wrote in news: snipped-for-privacy@4ax.com:

replacing

First off, I didn't intend the comment to be taken quite so 'literal'. The reason I mentioned valve guides, were the EFFECTS that can occur because of them. The valve guides would be a ROOT CAUSE for an EFFECT, such as below: A) Introduction of oil into the combustion mixture, could be fouling the O2 sensor. B) If bad enough, dropping vaccuum below expected levels for the conditions (MAP) C) Cause a temporary misfire in one or more cylinders from a fouled plug. From my experience, most newer vehicles will fault the check engine light on a misfire. Don't ask me how they detect it, but the codes show they can detect a misfire in each individual cylinder.

Unlikely, its really gotta be burn'n some friggin oil before the O2 sensor will foul, the temps at that location (where the O2 sensor is) is to darn hot, the oil turns to soot and is blown out before it get to the O2sensor.

Again, if its burn'n that kinda oil a check engine light is the least thing to worry about :-)

Gotcha :-)

I need to replace to stinkin valve guides in my Montero, darn thing runs like a top, doesn't smoke unless I let it idle for a while (more than 5 minutes) then it smokes (bad) for a few minutes (like the way they do if the valve seals are bad) I'm not looking forward to this job. It seems like every time I pull a mitsubishi head, I find a crack, so I have a feeling that I'll be buying a new set of heads (why did I learn this trade). Maybe I'll get lucky this time (I hope).

On Tue, 13 Apr 2004 15:29:52 -0400, North shouted from the rooftop:

And everybody blames the electronics first without putting a vacuum guage or a leakdown tester on the engine or pulling a fuel sample (at $2.39 a gallon, I'd be suspicous of a gas station owner 'stretching' the fuel stock). A plugged converter will cause a loss of economy and my toss a EGR or O2 code. So will a missing block ground wire. A corroded starter solenoid terminal wire will kill the keep-alive power. Codes won't stay set and the EEC-IV processor will be in learn mode at every start up. Older EEC-IV boxes can't detect a missfire other than as a rich condtion, which will force a lean map and set a code. How's the plug wires? Using anything other than Motorcraft plugs can do screwy things to the 3.0 engine.

-Carl "An honest man doesn't need a long memory"- Jesse Ventura

The O2 sensors are a whole lot more standardized than spark plugs, which have numerous electrode setups, various heat ranges, a whole slew of thread lengths, and several thread sizes ans well as 2 sealing designs (tapered seat and washer)

O2 sensors virtually all use the same technology, outputting the same voltage for the same oxygen level in the exhaust. A heated sensor can be used in place of a non heated, and any 1,2,3, or 4 wire sensor can be used in place of a single wire.

What's more, by far the largest majority have the same 18mm thread, so are basically universal fit. You can buy universal sensors without plugs that will fit just about anything at any parts supplier. As for used sensors, if you can get one with 30,000 km on it for $2, use it. A new one will be roughly $15-$100 depending where you buy it, and the chances of getting a bad one fresh out of the box is just as high as getting a bad used one. The used one has been proven to have worked at some point - That's why they are called "experienced" parts.

Around here, southern Indiana, several of the car parts stores will check the codes for you for free. They'll also check batteries, alternators and starters if you'll carry them in the store. Heck, if they're not real busy they'll run outside and install small things: wipers, headlights etc.

Some Japanese vehicles with 3- or 4-wire oxygen sensors need a replacement having a high resistance heater wire or else the vehicle's computer may be damaged.