I just converted my '90 to use a 4-wire o2 sensor instead of the 1 wire sensor it came with. With another car I used to have I converted to a 4-wire setup to fix a rough idle and it worked great there so I figured it might help on the teg too. The difference was night and day, I can’t even feel the engine running now until I turn on the a/c and even then it’s nothing like it was. Anyway if anyone wants details let me know, the way I did the setup was pretty much plug and play so I can undo it later if I want to for some reason…
sure fill us in. i think theres a thread where 91integGS did the same thing. reminds me of when i was running the 450 injectors with a manual map hack and how extremely sensitive the idle was to changes. i’d try it but my current sensor is still pretty new. ill keep an eye out if i see one for cheap…
wow, I am interested in that! how much is a 4 wire o2 sensor? do a “how to” please
what do you think the reason the car would run bad?? i replaced the regular sensor before and honestly felt no difference. And i also was geting like 20-21 mpg… sucks but what do you think could cause it =po… i would like to know cause i am going wideband and it’ll be using the 4 wire with a narroband output to the ecu =p
my search didn’t come up with anything, but i’m pretty usre i’ve seen a writeup on this procedure on here before.
http://www.g2ic.com/forums/showthread.php?s=&threadid=44600&perpage=20&highlight=4wire&pagenumber=1
its in there somewhere 
First off, this mod will only have a chance of helping if you’ve taken care of everything else first, all the tune up parts, motor mounts, etc. I’m not sure why exactly it works but i’ve seen it help and seen others convert and have it help. All I can figure is the more exact O2 readings compensate for fuel injector wear and a degraded ground through the exhaust system(the 1-wire O2 sensor uses the exhaust for the ground), but maybe someone here knows for sure why…
Anyway I used the Bosch 13275 sensor. This is not the universal 4-wire sensor, it crosses to some early-mid 90’s Dodge cars, the Intrepid is one of them. I use this 4-wire O2 sensor vs. any other because it is always in stock at just about any decent parts chain, and it’s ~$41 vs. > higher. If someone can find a cheaper one let me know, it took me forever to find this one and most 1-wire sensors go for almost this much. You can use almost any 4 or 3 wire heated sensor you want though. If you want a plug and play setup like mine you will need an oxygen sensor male and female harness pair from any junkyard car that had a 4 wire sensor. If you can find a 90’s intrepid with the O2 connector still in it you’re one step ahead of me and won’t need to do as much work. I used some Hyundai harness because that’s all I could find, but this harness was used on Mitsubishi’s as well. Again this is personal preference, in the past I have used GM weatherpacks for this purpose.
Then you will need a male and female bullet connector, a couple feet of ground wire and a few inches of some other wire, a loop crimp connector(can’t remember what it’s really called right now) that will allow a 12mm bolt to fit through it, wire stripers, crimpers, and a soldering iron, solder and heatshrink(or crimp connectors if you want to go that route)
On the Bosch sensors, the two white wires are the heater, the gray wire is the signal ground and the black is the signal.
When I was deciding how what all the wires did I found it easiest to plug in the harness connectors as O2 engine harness will probably not have the same colors as the Bosch O2 sensor will, and this will help keep them straight.
If you have the Bosch 13275 and have a different engine side harness you will need to cut off the connector it comes with and solder or crimp the O2 side connector you found at the junkyard onto the sensor.
Remove your current O2 sensor and cut off the plug leaving a few inches of wire on the plug side. You want to solder or crimp the connector you just cut off your old O2 sensor onto the signal wire of the O2 engine harness.
Then you will need 2 lengths of wire a few inches long. One wire is going to one of the heater wires on the O2 engine harness, the other two get the bullet connectors. Directly below the original O2 sensor connector are two wires, one yellow, one some other color. This is your reverse lights switch wiring. If you’ve got an auto it will probably be a little different, i have not had time to research that though. Anyway disconnect the Yellow wire and connect your bullet connectors inline with it. You are basically tapping power from the reverse lights circuit. Why? It’s conveniently located, it’s only powered when the car is on, it’s a fused circuit(always a good idea) and the circuit is not used most of the time. I was worried about blowing the 10 amp fuse that is on this circuit but so far it’s been fine, i’ve left the reverse lights on for a while with the ignition on and the fuse hasn’t blown.
Ok at this point there should be 2 wires left on the O2 engine harness. One is the heater ground, the other is the signal ground. I connected these two together and ran one wire to a convenient ground. Some say you should run the signal ground to a different ground but that’s up to you, personally I don’t see why it would matter if your ground is good. I ran my ground to the clutch cable bracket on the transmission. This is also where the battery ground cable connects so it’s about the best ground on the car. I ran my loop connector under one of the other bolts though because I didn’t feel like resetting my radio and reteaching my car how to idle.
That should be it, I would plug in the new O2 sensor before installing it and make sure it heats up when you turn the car on. If it doesn’t there may be a problem with the wiring or the sensor. I used some wire loom to hide and protect my wiring.
If something didn’t make sense or is confusing let me know, sorry this took a while i’ve been on vacation this week!
i think the main reason why its better is because its a heated circuit. o2 sensors work most accurately in a specific heat range. with our 1wire, heat fluctuates greatly based on engine load.
That is one reason I had heard, especially at idle the temperature of the sensor will cool off and the output will become erratic…
Originally posted by XDEep
sure fill us in. i think theres a thread where 91integGS did the same thing.
That would be me! 
And the difference is even better if you have an aftermarket header where the O2 sensor is just before the cat… The sensor needs to be at operating temp to give good readings…
archivethis
Good stuff guys.
Later,
BR
bookmarked
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so which wire connects back to the ecu?