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Oxygen Sensor- Replace?
I'm not sure about the age of my O2 sensor. Older than 60k I think but I don't know after that. Lifespan is 80k I think, and the owner then did most required maintence from what I can tell so it might still be good but I don't know.

The engine ran rich for a while, does this foul the O2 sensor like it does the spark plugs? Definitely going to replace if so.
1993 4 door JX 16v fed manual all stock
great quesiton.
the carbon can burn off.

but there is this odd, chicken and egg thing sometimes.
the blanket effect. the carbon covers the 02. element, blocking all actual oxygen there. telling the ecu its rich (fibs). this can cause it to cycle , too rich then too lean.
could happen say if FR reg goes nuts stuck at 60psi. engine misfires rich but the 02 is hopeless to read right ,

the top reason for 02 failures are, besides 100k mile end of life. suzuki shows tad less for 8v, i dont believe it.
is additives added to fuel (many) not from fuel/gas company. Techron is ok, but those others? ive seen purple colored 02 elements,. what that crap.?
exhaust leaks (cracks) near it.

you can get a cheaper 02 , using the univeral kit, its not hard, or less good.
bosch. 15730
the 4 means 4 wires. my added. number

34 bucks at amazon
or 29 on fleabay


such a deal , no? not big bucks, at all.
i can match any wire color too, just need to know if yours is 3 wire or 4, fed or calif.
the universal works for 3 and 4 wire. too.
its only cheaper because there is no factory PNP connector, its not lesser.

my colors chart is here


i even tried a $20 delphi 02 and it ran like a champ. (correct pn , sure)
Interesting. If the engine was cycling rich/ lean, how long would these cycles last, hours, minutes? The manifold is cracked, which I think could have set it off. (I was considering replacing the O2 sensor at the same time as the manifold hence the original question).

I did notice the engine has several distinct "modes" of idling. Sometimes it is at about 800 rpm and the rpm plunges maybe down to 700 or 600 (hard to tell on the tach it's pretty fast) and immediately goes back to 800, this happens regularly a bit more than once a second, it sounds like the engine is revving. The other idle "mode" is way high like 2k rpm but steady. Is this from cycling rich/lean?
1993 4 door JX 16v fed manual all stock
it is very hard to diagnosis any pre OBD2 car, made. OBD1.
no scan tools.
with a scan tool, all this is in view, live.
the outside air, is 20 % oxygen
even a small crack in the exhaust will make the 02 slam to 0v. Even 1% air leaks. the outdoor air is 20 times, more than that. ( like dumping a bucket of water on a burning candle , bam)

the O2 sensor is a switch, it's not linear. (unlike modern wideband sensors are)
so, if the ECU sees this sensor at outside 20% air, it slams to 0v (0 means the sensor sees lots of 02)
the ECU sees that, and stupidly (OBD1 is dumb) and forces the injector huge rich. (in fact to much , corrected in OBD2)
(Chaos, is hard to imagine and explain)
This is all about FUEL TRIM:
so now it's rich, and may(will) misfire. adding more 0xygen for that (caused by cylinder air slugs) the extra 02 , makes it even worse, this is the Achilles heel of all old cars.
Misfires, is like the Prize fighter slugging himself. silly. there must be no air leaks, period. or it will go nuts.

Slug my face mode 2:
now if it goes to "Bosch, white paper, hell mode." (my name) the carbon places a blanket of carbon over the tip. this can now SHIELD it from that oxygen.
this causes the 02 sensor to stick at 1v. (ECU cuts fuel and the blanket now burns off and .... )
the process then repeats, over and over, CHAOS mode. how long , depends on how big that air leak is.

2k RPM? HOT? never.
but sure cold that is the IAC doing its job. to do just that.

the hot idle surge, can be many things, a huge list.
but if engine has perfect compression , only a few things.
egr leaking (main)
the 02 CHAOS mentioned above.
leaking injectors
clogged (or partially) injectors.
induction air leaks. of any kind,
even a bad MAF, tap on side gently does RPM change, that be bad. (stock intake,,CAI hacks may do this, most CAI hacks usually beat the MAF to death.)

if car was OBD2
you'd see
1: closed loop dead, it idle
2; 02 going nuts, (plotted live)
3: LTFT , way the H3LL off, not near 0 but say, -40% one minute then +40 next or its DEAD. FUEL TRIM !

if no scan tool , i use a real scope on the CELL+- pins of the 02.
and watch cross counts.
if its not like this , i fix that first.
hot idle.

if it don't swing or is shifted, off center the o2 is bad, or there are exhaust leaks or other causes. there is an error here, see .090 he put the decimal point wrong its 0.9v 9/10s of a volt.
[Image: O2-dso-real.jpg]

my newer car can swing 6 times a second, at hot idle.
the limit is the speed of the ECU, on old cars, they are slower. (slow 02 sensors waste fuel, they all do that when old)
what you are seeing here, is the ECU hunting STOICH,
Stoich is at 0.45v average. or 14.7:1 AFR ratio.

the ECU must hunt it fast, because the sensor is not analog, it's a switch. lean, rich, lean , rich; switch
this hunting is called CLosed loop. this is because it's a closed loop servo system.
like an auto pilot in an and air craft.

the ECU works real hard, moving fuel trim to keep the AFR at STOICH, by fast hunting the fuel trim. and reading the O2 over and over. in a software loop
the above plot is the results of fuel trim, and the resultant oxygen remaining in the exhaust stream.
the ECU can not measure fuel mix at all , only 02. its an indirect method and does work.
Thanks for all of the information. I realized that at this point, there are enough problems that it's hard to sort out what's really going on with anything. Right now I'm replacing long expired parts, fixing obvious problems, and doing general tune-up work. I'm going to come back to the O2 sensor and anything else that is still questionable after getting the obvious stuff sorted out.
1993 4 door JX 16v fed manual all stock
Good evening, I have been reading the Oxygen sensor section in the Fixkick site but I decided to post here to make sure I buy the right O2 sensor.
Suzuki Sidekick 1.6i 16Valves - 4 doors 1992......I don't know how it ended up in Europe (it really is a Vitara but is identical to a Sidekick).
The O2 sensor was never replaced in this vehicle in 23 years so I'm thinking of buying one from the internet.
It has 3 wires (pink, purple and black).
The connector is 4 pins, with 1 empty connector.
I attach photos of the male and female connetors.
I'm hoping to find the right sensor/connector in Europe (like I managed to do for many other parts) as shipping costs from USA are often more than the cost of the spare + $50 custom charges, so maybe some codes (oem code or Bosch or Denso codes) would be very useful for me.
The only spares I could not find in Europe so far is the front signal light lamp, next to the headlight lamp (Vitaras have the 2 light in one single lamp) and the front fender because the side signal light is at the front of fender, while Vitaras have it near the door.
Thanks for the help

Attached Files Thumbnail(s)
first is , pnp or universal fit, the univ. is just wires no custom suzuki connectors.
the bosch pn are same
as here ,

see my matrix here.

15726 hand wired
15701 PNP

pnp means plug in and it plays.

in Europe the name is lamda sensor. same part.
Found it! plug and play Bosch 15701.....Sensore Lambda yes!!
Big thanks!

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