Can't find the 02 sensor

[Skelt11]

So I'm trying to replace the 02 sensor in my 87' and can't find it anywhere. I've checked the exhaust manifold on both sides, the exhaust pipes all the way down to the muffler. Where is it supposed to be?

 

[BroncoJeff]

Its supposed to be where the pipes come of the manifold and meet, it looks like a spark plug with a wire on top.

 

[Broncobill78]

This is NOT an easter egg hunt. You have a Y-pipe that leads down to a catalytic converter and then the rest of the exhaust. I have an 88' and the O2 sensor is right in front of the cat. Search the Y-pipe & the area in front of the cat, you *can't* miss the **** for it and if there's nothing installed in the **** then you'll certainly be hearing it when you drive. I absolutely promise that there's only ONE sensor looking thing screwed into the exhaust system between the engine & the cat and that's the O2 sensor. Might be that someone else removed & plugged it but the **** will still be there (unless the exhaust has been replaced and the **** excluded)

 

[crazyhorse85]

LIKE BB78 WAS SAYING SHOULD BE RIGHT BEFOR THE CAT...IS THE CAT STILL THERE ? UNLESS SOMEONE DELETED IT WITH NEW EXHAUST SHOULD BE A 2 OR 3 WIRE PLUG HANGING AROUND UNDER THERE IF IT'S BEEN REMOVED AND PLUGGED OR LOOK TO SEE IF A SECTION OF PIPE HAS BEEN WELDED IN...WHICH MEANS SOMEONE CUT IT OUT..AND IF YOU'RE LIKE SOME WE LIVE IN EMISSION STATES, AND YOU PLAN ON A DAILY DRIVER THAT STUFF WILL HAVE TO BE PUT BACK IN....GOOD LUCK, HOPE THIS ENLIGTHENS THINGS A LITTLE BETTER FOR YA.... >-

 

[Skelt11]

Thanks guys. I've looked all over the exhaust, both headers, and manifold and found nothing. It must have been removed. I live in NC and since its older than 96 I don't have to worry about emissions. Will not having it hurt my mpgs?

 

[Broncobill78]

Yes. By not having the O2 sensor you force the computer to operatin in "open" loop mode as opposed to "closed" loop. When it's in closed loop the computer knows how much fuel it injects to each cylinder each cycle and it then compares that to what the O2 sensor is reading for emissions. When the sensor tells it that you're running rich the computer dials back the fuel rate, when you're lean it up's it. Without the sensor the computer has no idea what the exhaist makeup is and all it will do is inject a baseline fuel rate & hope for the best. Now just HOW much it's effecting you milage is anyone's guess but it IS effecting it.

As a sidenote, not getting any reading at all from the O2 sensor should definately illuminate the MIL, if your CK Engine light ISN'T on 24/7 then the previous owner got tired of looking at it and removed the bulb OR he got in there and made some other changes as well but not having an O2 sensor at all should trip the MIL, if it isn't you have other issues as well.

 

[Skelt11]

Yes. By not having the O2 sensor you force the computer to operatin in "open" loop mode as opposed to "closed" loop. When it's in closed loop the computer knows how much fuel it injects to each cylinder each cycle and it then compares that to what the O2 sensor is reading for emissions. When the sensor tells it that you're running rich the computer dials back the fuel rate, when you're lean it up's it. Without the sensor the computer has no idea what the exhaist makeup is and all it will do is inject a baseline fuel rate & hope for the best. Now just HOW much it's effecting you milage is anyone's guess but it IS effecting it.
As a sidenote, not getting any reading at all from the O2 sensor should definately illuminate the MIL, if your CK Engine light ISN'T on 24/7 then the previous owner got tired of looking at it and removed the bulb OR he got in there and made some other changes as well but not having an O2 sensor at all should trip the MIL, if it isn't you have other issues as well.

I'm going to talk to the guy who is doing my exhaust about putting a **** in for it and I'll have to research how to rewire this thing. I have to say, someone has rigged this thing up pretty good. It runs great (well, did before I started swapping carbs..) its just that the gas mileage for it sucked. I'm going to keep looking for the 02 sensor, I'm probably missing it.

 

[Jersey]

I'm going to talk to the guy who is doing my exhaust about putting a **** in for it and I'll have to research how to rewire this thing. I have to say, someone has rigged this thing up pretty good. It runs great (well, did before I started swapping carbs..) its just that the gas mileage for it sucked. I'm going to keep looking for the 02 sensor, I'm probably missing it.

Theres why you cant find it. Its carburated. O2 sensors help regulate the air/fuel ratio in Electronic Fuel Injection. Carbs have adjustment screws for this, and dont use the sensor. But on another note, my 96 has EFI, runs like a dream, is bone stock save for the 33" tires, and gets an outstanding 10.5 miles per gallon. Guess you cant win um all huh?

 

[2NDTOUR89]

I may disagree on the no o2 on carb engines. My 81 had an o2 sensor on it and it was carbed, the o2 also fed info to control spark advance on the early computer controlled engines that were not injected. On that note, an 87 should be injected so if you have a carb, chances are that it really has been "rigged" as you put it. Not saying that swapping out injection for carb is rigging anything, lots of guys do it, however you may have a ride that has had more hacked out of it before you purchased it and did not know. Since 86 if my memory is right, the f150 platform (1/2 tons including Broncos) with the small motors were all injected, it was only the 400-460 that remained carb.

Just my 2c.

 

[Broncobill78]

Yup, I'd stop looking for the O2 sensor right now before you waste anymore time. An 87' was most definately an injected truck. If you bought this thing with a carb on it then a previous owner either swapped the EFI for a carb or replaced the entire engine with a older/rebuild carb'd engine. Swapping from EFI to a carb isn't rocket science but if *I* were doing it (especially if it were a 20 yr old truck) I'd just swap in a new engine & call it a day. There are a lot of sensors to be removed & rewiring that has to happen, swapping in a complete *sensorless* engine takes a lot less time, hassle & bull$hit. With the engine out it would have been a simple job to change the Y-pipe which is what must have happened if there's no **** there for the sensor because an 87' DID have one.

If the engine has a carb then chances are that you DON'T need an O2 sensor. You'll have to ck to see if you're running a processor but I'd bet good money that the prev owner simply dropped in a carb'd engine and called it a job well done. Understand that this will require a little investigation. He *might* have been the kind of guy who like to do a complete job and he pulled the processor & all the extra wiring out OR he may have just cut the leads to every sensor he found and left the processor right where it was. The 87's were the first of the multiport trucks & I honestly don't know if they used a seperate sensor harness like the newer trucks (and truth be told I'm simply no ambitious enuf right now to go climb all the way up into my 88' to ck). If they DID have a seperate sensor harness then he may have simply removed it where it split from the main. Either way I'd examine the main harness foe evidence of numerous cut wires (but, then again, if he was **** enuf he would have taped & re-loomed it afterwards to achieve a stock looking engine compartment)

Is the ck engine light on ? If it's lit then you still have a processor in the truck if it isn't then he either removed it or disconnected it because that's about the *only* way to keep the MIL from illuminating after swapping to a carb (unless as mentioned above he did a fair ammount of rewiring). With a carb on the truck the processor isn't getting info from a whole host of sensors and there's just no way the light wouldn't be lit.