Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

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Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

December 14, 2005, 03:32:22 PM

'87 3.8L

My mileage has dropped a good bit since it got cold and I think a fair bit of it is the lack of heated O2 sensors. This has me interested in installing 4-wire O2 sensors in place of my 1-wire sensors. I thought of just going to 3-wire, but if I'm going to do it, I might as well go all the way. I have a few questions though.

Later model Thunderbirds/Mustangs came with two kinds of 4-wire sensors. Bosh # - 15716 or 13127. The only difference I can tell is the price. The 15716 is $44.89, the 13127 is $60.99 (partsamerica prices). Any idea on any other differences? i.e. switching rate, heater resistance, longevity...

What is the resistance of the heater? Google searches have shown it to be ~4-7 ohms, which equates to a worst case of 7.2 amps. Anyone have any more concrete data?

Also, when does the EEC begin to use the O2 output? I've read several different things. From just a timer, timer + a minimum ECT, minimum ECT and so forth.

http://griffshp.com/belchja/forums/oxygensensors.xls

I plan to buy harness adapters from fordfuelinjection.com ($15/ea.). The heater input will be fed from a relay that gets its trigger when the ignition is "on". The signal ground will be run to the EEC EGO GND (anyone know where these are located?)

Anybody see any hidden pitfalls in my plan?

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #1 – December 14, 2005, 04:51:19 PM

I would stick with the 3 wire sensor. the 4 wire provides you no benifit. On a 4 wire o2 sensor car, I'm thinkin hard and may be guessing that the computer controlls the ground as well. For a cleaner signal. With the newer cars having two sensors, one sensor is for pre cat, the other is after cat. Why they are two part numbers I dont know but I do know the tips are shaped differn'tly.

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #2 – December 14, 2005, 04:52:57 PM

Oh I forgot.

The computer utilizes the o2 sensor when it detects the voltage changing. I guess the sensors are bumps on a log before they get hot.

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #3 – December 14, 2005, 05:11:57 PM

Quote from: CougarSE

I would stick with the 3 wire sensor. the 4 wire provides you no benifit. On a 4 wire o2 sensor car, I'm thinkin hard and may be guessing that the computer controlls the ground as well.

4-wire O2 sensors have the signal ground either run to the SIG RTN or a dedicated HEGO GND wire depending on the car. My '87 3.8 has an EGO GND wire for each sensor. If I hooked up the signal ground wire from the O2 to the EGO GND, I would get a better ground. It probably isn't much, but if I'm already going to be splicing and dicing, two more wires won't hurt.

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #4 – December 14, 2005, 05:18:24 PM

Three or Four wire it don't make any difference as long as the ground is good on the exaust manifold back to the EEC... They went with the four wire to help eleminate poor ground issues... I used a four on a three, just cut the ground wire and clamped it to the body of the sensor with a small hose clamp(no I ain't beyond "riggin" as long as it ain't my car)...

The price difference is likely the difference in the small pencil sized sensor vs the larger thumb sized unit.

Using a relay to power the sensor element is a good idea. It feeds from the ign sw on the 5.0 units, prolly helps contribute to switch failure... The EEC ground is pin 49 orange wire(at least on '86 & '88, I don't have a '87 EVTM). I'd connect the o2 ground to it, but be sure to leave it connected to the chassis...

EDIT... Dragged out the '87 Emissions Manual... Ground for the o2s are listed as pin 49 sensor one(29 sensor output) and pin 44 for sensor two(43 sensor output)

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #5 – December 14, 2005, 09:41:54 PM

Hmm, what about planar sensors?

http://www.forparts.com/Bos02update2.htm
http://www.delphi.com/pdf/ppd/sensors/et_oxy_planar.pdf

It is fully fucntional within 10 seconds and has the same response curve. It also uses less power (<1.7A). They were used in 96-97 3.8L Tbirds (among others).

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #6 – December 21, 2005, 02:52:08 PM

Hmm, seems we have a correlation between ambient temperature and fuel economy for my drive to work. (7.6 miles, ~13 min)

For reference, in the summer...I got around 25 mpg for the same trip.

Tripminder = teh win

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #7 – December 21, 2005, 03:43:29 PM

I'd be interested to see if you see any gain in this.

I asked a similar question a while back when I still had the turbo Ranger. It was a single-wire O2 as well. I got more of a "It won't matter" reply, and I had other things to do, so I never messed with it.

Also, your milage is going to drop some if you let the car idle a bit to warm up. Since you're in AL, I'm sure you don't see too many days, or at least any woth letting the car warm a bit.

When I build the 2.3T for the Z-7 I'm going to lean towards the "driver" approach and not the "racer" one, and will trying a couple things to boost effeciency and mileage while still maintaining a good solid useable power base.

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #8 – December 21, 2005, 05:17:32 PM

A heated sensor in the stock location will not have any benefit except it will help the car go into "closed loop" mode faster. Once the exhaust is hot, it will be hotter than the O2 heater could ever make it. If you make frequent short trips you might notice a small gain, but if you usually drive the car until it warms up you won't. Heated O2's exist for cold emissions to get the O2 heated up faster so the PCM can start using the data (ie "closed loop", where the PCM reads O2 data and adjusts the A/F ratio accordingly). In fact, now that I think of it, your factory PCM is probably programmed to ignore O2 data until a certain set of parameters have been met (coolant temp, time since started, etc), so a heated O2 probably won't help at all.

Now, if you relocate the sensor downstream (such as if you install long tubes or Mustang shorties) you might see a difference...

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #9 – December 21, 2005, 08:38:51 PM

Most of the time those Bosch O2 sensors are offered in the factory style with the factory plug and the other most likely has the universal conector. they charge more for the universal because they send you 4 posi lock and a neat cover for them.

Oxygen Sensor Upgrade Questions (1 wire --> 4 wire)

Reply #10 – December 21, 2005, 09:41:54 PM

I plan on buying a set of factory 4-wire pigtails ($15/ea.) and std. Bosche 4-wire planar sensors.