Oxygen sensors, Fat vs. Skinny

[LA_phantom_240]

Is there any difference in the fat and skinny oxygen sensors on a KA? Reason I ask is that the factory oxygen sensor after the cat on my s14 is a skinny type, but my DC header is threaded for the fat type of o2 sensor. Being a three wire o2 sensor, I know that the s14s built after 03/1995 have a three wire fat sensor before the cat. Is it okay to interchange the fat primary of the later s14s in place of the skinny secondary o2 sensor on my header?

[murda-c]

Damn i was about to make an adapter for my skinny one...lol

What are you gonna do about throwing codes?

[Addicted2Kouki]

The fat one before the cat controls how the car will run when cruising and part throttle acceleration.

The 2nd one after the cat measures emissions and does not affect how the car will run.

[LA_phantom_240]

So in all actuality I can run without my second o2 sensor? I have a fat 3 wire in there now, been like that for like 3 months... With my recent cutting out issue, I ran my codes and one of them is my second o2 sensor, so I thought maybe it needs a skinny instead of a fat. It seems like fat or skinny it doesn't really matter though.

[projectRDM]

Secondary O2 sensor is for diagnostics of the catalytic converter only. It DOES NOT affect engine operation.

Same thing that's been said for nearly 15 years.

[LA_phantom_240]

Secondary O2 sensor is for diagnostics of the catalytic converter only. It DOES NOT affect engine operation.

Same thing that's been said for nearly 15 years.

Good, so that's one less CEL code I gotta worry about.

[burnsauto]

they do make spacers for the o2 sensors. (i MAY have one..)

if not, enjuku sells them... last time i looked.

[98s14inaz]

Put a bolt in the bung and ziptie your sensor under the car somewhere. As long as the sensors have different signals you will not throw a code. Like everyone else said, first one tells the car how to run, second tells the car that the cat is working.

[burnsauto]

now will this effect passing smog?

[98s14inaz]

now will this effect passing smog?

In california, yes. The very fact you have a header will fail you. In Arizona? No.

[projectRDM]

now will this effect passing smog?

If the sensor is unplugged you'll throw a CEL, which will fail on OBD-II cars. On OBD-I cars where they only run a sniffer it doesn't matter as long as the cat is working. OBD-I emissions testing doesn't check for a CEL or stored codes.

[98s14inaz]

If the sensor is unplugged you'll throw a CEL, which will fail on OBD-II cars. On OBD-I cars where they only run a sniffer it doesn't matter as long as the cat is working. OBD-I emissions testing doesn't check for a CEL or stored codes.

Truth. The reason I said what I said is because I try not to have codes even on my obdI cars. But yes, I've passed the sniffer in AZ with a cel light on. Every state is different though.

[LA_phantom_240]

In california, yes. The very fact you have a header will fail you. In Arizona? No.

I thought the DC headers were pending CARB approval. Guess not lol. Doesn't matter, Cali is gay on emissions and I live in Louisiana

[D.Bo]

its doesnt matter if its fat or skinny they do the same things. only diff is the size of it. so you could but a fat o2 where the skinny 02 or vice versa..

[!Zar!]

I think the only difference between fat and skinny is that the skinny one only sends information one way.

And the fat sends information as well as receives it.

Either I had a dream about this or read it somewhere...

hahah.