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86-95 Trucks & 4Runners 2nd/3rd gen pickups, and 1st/2nd gen 4Runners with IFS

O2 help

Old 12-17-2007, 08:05 AM
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O2 help

Hey all,

I bought a 86 RTE from a a kid that cannot get it to run right, runs OK utill it starts to boost the misfires and sputters. So I get to looking around and the O2 sencer is not even hooked up. The plug it supposed to plug into is gone so which wire is it supposed to hook up to. Found 3 posibilities. One on left is shielded like a coax cable. One in middle is green with black stripe. one on right is a 2 wire with a T plug. Which one is for the O2 and what are the others for? Thanx, Pugi

Old 12-17-2007, 09:19 AM
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I'm not positive but I think it's the two without plugs. One "hot" and one "ground" the other with the plug may be to something else. How many wires are on the o2 sensor?
Old 12-17-2007, 09:33 AM
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Originally Posted by Hoopster
I'm not positive but I think it's the two without plugs. One "hot" and one "ground" the other with the plug may be to something else. How many wires are on the o2 sensor?

O2 sensor has just one wire, I pretty sure is not the one with the plug. Now which of the remaining 2 is it? My guess is the one that is shielded, but that is just a guess. Pugi
Old 12-17-2007, 10:42 AM
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Could someone look at the wire that plugs into the plug on the thermostat housing. Mine is not plugged in and I think I found a wiring diagram that shows a green with black stripped wire that goes to the water thermo s/w. Could this be that switch and that wire? Be a big help if someone looked really quick, thanx Pugi
Old 12-17-2007, 07:20 PM
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Sorry, I don't have an '86 so I don't want to mislead you but you're probably right guessing it's the shielded wire for the o2 sensor. Hopefully someone else can help more.
Old 12-17-2007, 07:43 PM
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On a '90 and a '96 there are 4 wires running to the O2 sensor.

1 shielded from the ECM to the O2.
1 ground from the intake manifold (source point may not matter to much)
1 12v provided from the EFI relay
1 from the HT pin on the ECM. I presume that is the wire to heat up the O2.

Also, there is wire that wraps around the shielded wire. This wire ties into the ground wire from the intake.

You won't find a plug in the engine bay for your O2. Any plug that was once there would have been right by the O2 itself.

Most likely you'll need an EWD for your year vehicle and start tracing wires back to the correct pins on your ECM.

Of course, your problem may not be steming from a non-existent O2 at all, but might as well start trying to figure out the wiring and get it connected.
Old 12-18-2007, 07:18 AM
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Thanx for the help guys....Pugi
Old 12-18-2007, 07:35 AM
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Wait a minute the o2's ground thought the intake manifold........?
am i reading this correctly here or what?
If this is the case i am going to go run a new grd lead off the battery to the intake manifold and see if that makes any difference.
Old 12-18-2007, 07:45 AM
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Originally Posted by nate V
Wait a minute the o2's ground thought the intake manifold........?
am i reading this correctly here or what?
On my '90 and '96 they do. This might not be the case for all years however.
Old 12-18-2007, 09:28 AM
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humm............
definitely my engine is included in those years so maybe I will give it a try.
Where on the intake manifold are they grounded to?????????
Dont mean to steal your thread there bud but this is just good information here
Old 12-18-2007, 10:41 AM
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On the '90, ground point EC is located at the rear end of the intake, PS. From the diagram, looks like somewhere near the fuel rail.

On the '96, ground point EC is located on the DS of the intake, above and just behind the alternator.

There will be maybe 5 or 6 grounds attached to point EC on either engine.

Majority of the wires will be BR (Brown).
Old 12-18-2007, 02:59 PM
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Hey thanks for the info
What do you mean by EC? Engine Control.....

Im going to run a ground from the battery to the top of the plenum tomorrow or something. Need to find a new alternator first though.
Old 12-18-2007, 04:20 PM
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Originally Posted by nate V
What do you mean by EC? Engine Control.....
EC is just what that particular ground point is labeled on both EWD's. It would make sense that it stands for "engine control", as it does seem to provide several of the grounds for the ECM, O2 and related engine components... but that would only be a guess.
Old 12-19-2007, 05:14 AM
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well thanks for your help sounds like that is where i will be headed next. did i mention i hate wiring.
Old 12-19-2007, 11:01 AM
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Nate dont worry about the hijack, As long as good info here is helping someone I'm cool with that.

This is now project "OH CRAP" Because everytime I turn around " OH CRAP there is another problem"

New question....The idle adjustment screw rests against a vacuum selenoid ( i dont know the name ) Where is this selenoid's vacuum hose suposed to be connected?

Old 12-19-2007, 04:34 PM
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Originally Posted by PUGIDOGS
New question....The idle adjustment screw rests against a vacuum solenoid ( i don't know the name ) Where is this solenoid's vacuum hose supposed to be connected?
If you post a pic of the part(s) in question, you might have some answers pop up.
Old 12-20-2007, 05:47 AM
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Yea a pic would help
is it a 22re or a 3.0???
dont really have enough information to help you out here,

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