Test results for new universal O2 sensor
 

Awhile back someone posted a link describing a different universal Bosch O2 sensor that is equivalent to the OEM part. There was a Bosch engineer that looked into it and determined that it really was correct for the 944 NA. O2 sensor cost & replacement - Rennlist Discussion Forums

The part number is 15725. The Bosch long part number stamped on the sensor is different from the one on the Bosch Ford sensor that FRWilk recommended, which is what I was running previously. The Ford part worked ok, but the 15725 is awesome...and it only cost $40!

I've been running with no sensor plugged in since I finished the rebuild, since I was having some serious stumbling and missing problems once it warmed up that seemed to go away with the sensor unplugged, so the sensor may have just failed or maybe it was a totally unrelated problem with corroded connectors or something, since I also took a bunch of other wiring apart and tested stuff at the same time. The car ran good but seemed a little off in the part throttle, especially with the gutted cat Y-pipe. With no cat it smelled rich at part throttle and idle. I just swapped the new sensor in, took it for a drive, and it's night and day. The part throttle power delivery is definitely set right again and pulls even down to 1500. It's smooth as silk. There's no mild surging or inconsistent idling that I always seemed to notice with the old sensor, although that was also the old motor, meaning other factors could be involved.

The other big bonus is that it is packadged as a universal kit, so it comes with posi-lock splice connectors which are miles better than normal crimp splicers, most notably because they have an integral, ingeneous waterproofing setup to keep the splice connections clean.

YMMV, but highly recommended.

How about $20?

AMERICAN CARS 82-95 BOSCH 15725 UNIVERSAL OXYGEN SENSOR:eBay Motors (item 380163524363 end time Dec-28-09 16:35:53 PST)

I'm working on replacing my o2 sensor at the moment, I ended up with part number 13953; as per FrWilks guide, then found the new info about the 15725 part number; gonna go exchange the o2 sensor for the one that zucker/jason952 recommended, but while looking over at clarks garage I found that he has part number 15726.. is there a difference?

In the mean time, I posted a question about the actual o2 sensor connector at the engine bay harness.. http://forums.pelicanparts.com/5047505-post11.html

I need to know about the orage/single pin connector wire; as the previous owner removed this plug, and when I was looking for the place to crimp on the new signal wire, I was following the o2 sensor wire back to the harness, and the crimp on connector fell off of the fat green wire before I could get a good look at it.. The green wire I found under the connector, as listed in my question on the other thread, it's a coaxial cable, with center conductor, insulation, outer conductor maybe as a rf shield.. And the other question about the reference air, it appears that the orginal porsche o2 sensor signal plug at the harness is air-tight..
Ontop of this my green wire looks to be oil contaminated.. I need to dig into the harness to find some clean wire, to pig tail on a new section of wire for the new o2 sensor signal wire..

any info or suggestions appreciated, Thanks.

I have no idea what the differences are between the different model numbers. Could be anything from a different set of splicers to different protection tubes, ceramic, or heater wattage. I'll trust zucker since he worked for Bosch and would actually be able to cross reference the technical specs of the OEM Bosch to the equivalent universal sensor. There may be slight variations that won't make much difference, but the 15725 should be "right".

I have no idea about the early 1 wire sensor connector. Someone else may have some input. You may have to cut back the wiring to get to clean wire, unless there's somewhere before that for the sensor wires to breathe. The Posilock splicers are really convenient since they are easily disassembled. My kit came with four of them, so that last one may be handy for your predicament.

Thanks for the quick reply, I'll have to exchange the 12953 for the 15725 after reading that info from Zucker, I think it might have been a good thing that my sensor wire fell off before I could see how it was connected.. cause it would have been an issue to take back a o2 sensor with the plug cut off :P I haven't mounted/cut anything yet.. unless they can't get that 15725..

CA/USA export/ early car's have a 3 wire heated sensor, mine has the 2 conductor center green wire, thing, couple confirmations on my other question posted; about the same thing, center conductor is the signal and the outer conductor is just shielding, I figured that's how it was but thought I should get a couple second opinions.. I'll also probe for continuity at the conductor between chassis and the outer wire to verify if it's grounded/shielding...

The two wire heater plug with male/female to keep from hooking possitive/negative? or maybe to shield the hot wire, to keep it from contacting ground if it's unplugged. But the heater wires on the o2 sensor are both white, and no polarity indicators.. I'm guessing it's just a restive load heater =short and doesn't matter about polarity..

Correct. There is no polarity for the heater wires.

I had to have mine shipped as nowhere locally had one in stock, but Advance auto parts had the best deal on it unless you get one on ebay.

I am not an expert but I think the basic O2 sensor is very similar from one model of car to the next.

o2 sensors all have the same basic function and voltage levels back to the computer are all the same based on the chemistry of the standard gasoline molecule, and whether there is an excess or shortage of oxeygen in the exhaust gas. oxygen in the exhaust means a lean mixture, and when this happens, the sensor sends a higher than normal voltage to the computer, and the computer responds by increasing the amount of gasoline (ie richening the mxture)

Years ago the original sensors were one wire and the return current path is through the ground or threads. . In later years heaters were added to the o2 sensor to reduce emissions during warmup. these are the three and four wire sensors.

Since the burinng gasoline chemistry never changes, the guts of an o2 sensor are the same from model to model. The difference between a generic and "specific" o2 sensor is just the length and type of harness connector. And whether it has a heater element or not.

Since the voltage and current levels from the o2 sensor are very low and change very subtley it is important tu use the proper connectors, especially if the generic sensor is used. For instance soldering the wires to the old connector is not recommended as this changes the way heat folws thru the wires and throws off the sensor voltages. So follow the manufacturers recommendations on how to splice the generic connector.

I have been running a generic for years and I have no problems. There are many other variables that effect how a car runs or idles. Clogged injectors are one possible problem. Cleaning and rebuilding the injectors is warranted on an old car. This is an inexpensive process involving replacing o-rings and the pintels ( spray nozzels) and a kit can be bought for this. many performance shops will rebuild injectors and also flow test them. another possible cuplrit is weak spark, including bad wires, plugs or distrubutor cap. And another on the 944 specifically is the air flow meter. there is a procedure to remove the afm cover and clean the copper contacts with an eraser to improve the signal back to the computer. this is a 944 unique issue. another possible problem is leaks or cracks in the four large vacum lines from the j-boot to the idle control valve, and from the brake booster to the intake manifold. after replacing these lines my 85.5 pops over on the coldest of days and no warm up is needed. another area to check is the electircal system grounds at the battery and on the engine. weak grounds will show up as a stumble or miss at high rpm.

anyway, hope you are able to cure your miss.

So, I take it you didn't read the information from the Bosch engineer on the Rennlist thread linked to by the OP?

Thanks for the suggestions.. I'm working my way through all those little systems in regards to fuel metering, spark, intake/ vacuum actuated things, charcoal and vacuum lines are done, o2 sensor is done.... Next thing I need to check is the AFM, then I will look at the fuel/pressure/injectors. I have another AFM to try, before I pop the top on the other one, I want to see if there's a difference as my current afm has got water damage previously... I went through with the erasable pen type rubber eraser, it's got more grit than the pink ones. I already did the AFM update wire, even soldered bridge wires from the plug terminals to the circuit's on the ceramic board, to aviod an oxidized connection, or intermitten fault at that pressure contact area...

Spark seems to work fine on all plugs.. New cap/rotors/wires, plugs, except the plugs fouled within a week or two, due to the misfire/running rich... or maybe it is a weak spark all the time and won't fire off the gasses?? I dunno yet..

so did we determine if on the early 944's with the 1 wire no heater wire will work with the 15725? or do we need the 1 piece universal replacment?

I don't know if the 3 wire o2 sensor part number 15725 will work on the cars without the heater plugs. It should work, but might not be right, and may cause running issues if the exhaust gasses are not hot enough to keep the o2 sensor working right..

If you don't have the heater wires to power the heater "on early cars, it looks like a two way rubber insulated barrel connector coming out of the same wire loom as the o2 sensor plug, the heater wire has one male exposed and one female connector insulated and is next to the orange/single pin connector for the o2 sensor signal.. If you don't have the three wire setup on your early 944 then you want to get the 1 wire o2 sensor. In post number 27 by zucker at rennlist, zucker recommends that if you do not have the early car with heated sensor, use part number 11027, one wire o2 sensor.

One thing I did notice on the new part 15725 is that with the posilock fittings, the only place air could draw from in the connector body is through the plastic threads, around the center section, then through the other plastic threads, this would only be sealed from outside air if the black housing and rubber seals are used. I used all the seals/housing and stuff, but I didn't like that the only airpath was through the plastic threads, as they might be too restrictive, so I went ahead and drilled through the center conductor of the posi-lock using a small carb air jet drill, to provide the airpath through the center of the connector. Probly not going to make much of a difference, but atleast, according to their claim that the o2 sensor needs an airpath through the wire harness, I have one now.

$20 EBay unit arrived today, looking bueno!