Yamae

Yes, both RHD and LHD use the same O2 sensors.

MattLS400

Thanks Much!

So let me get this straight, my 1996 JDM CELSIOR carries 4 Oxygen sensors;

2 which are causative of rough idling and misfiring once faulty (PRE-CAT)

and

the other 2 which are responsible for the control of emissions (POST-CAT)

Question: These 4 Oxygen Sensors carries the same part number ? or is there a difference between the post cat and pre cat O2 sensors ?

LScowboyLS

when I go to amazon, it says it fits

regardless, the Nippon Denso website says it fits, that's what counts!

LScowboyLS

no the post cat and pre cat O2 sensors (upstream and downstream) are different part numbers as are the OE fit and universal fit (you want upstream OE)

the downstream (post-cat) sensors do not control anything, they are just there to tell on you to the authorities - lol (hence, "tattletale")

you could even disconnect the post-cat O2 sensors completely and the car would run perfect, but you would get a check engine light and a code

Yamae

I don't think so.

The ECU is designed to work the engine not too bad when O2 sensors are not working well. The ECU has a data table inside prepared for the faulty O2 sensor situations. It will supply almost proper amount of the fuel to cylinders depending on the air and the load. This causes some increase of CO, HC or NOx but the engine does not loose the power so much.

So average drivers usually seldom notice that O2 sensors are bad. Only the engine check light and the code reading are the way to know the bad O2 sensors. But when the ECU is not working well, there will be low possibility of the engine check light on and the high possibility of the rough engine running.

It would not be easy for you without knowing the fundamental knowledge and some Japanese language skill to maintain your car.

MattLS400

2 Upstream DENSO 234-4169 it is !!

You know, no wonder these O2 Sensors have gone bad.
The exhaust smells rich of fuel or carbon. But yet, its colourless. No smoke at all.

MattLS400

Just got them guys.

Any tips/ DIY manuals that I should know of before i attempt changing them myself?

deanshark

I think they're pretty much straight forward, take out old and put in new. I do know it would be easier with an O2 sensor wrench/socket which you can rent at any Autozone. When you unhook the wire connector be careful not to snap it.

LScowboyLS

yes, an O2 sensor socket is a must - and you might want to put some anti-seize on the threads to save some cussing next time, but just a tiny bit, if you get any substance on the tip of the sensor, you will ruin it

One side is much more difficult than the other, so don't get depressed if you happen to pick the hard side to do first! - lol

double check that you are replacing the sensors between cat & engine, it is very easy to get yourself turned around while under the car and accidentally replace the post-cat downstream sensors!

you might need to treat the thread with some PB-Blaster or similar chemical to break the threads loose - then whack them a bit ---- the keys to breaking something seized loose in a safe way is penetrating oil + vibration + time

I usually soak something like this for 12 hours in stinky PB Blaster before even attempting the job

MattLS400

Thanks ! Just as you indicated , one side was harder than the other. lol

From the pic below, I have changed the Oxygen Sensor between the cat and the engine.

After installing both, I pulled the ECU fuse, waited a min or 2, then took her for a drive till the engine warmed up again. But, The Problem Still Persists! I then brought her back in to run another Diagnostic Check, but now NO ENGINES CODES are appearing! ALL CLEAR!

Nevertheless, I do not regret changing my pre-cat O2s. As I believe I would realize the savings later on in increased Gas Mileage!

After having exhausted much options and already exhausted ! I decided to check the MAF.
(FROM POST #1)

With the engine warmed up, and intermittent rough idling occuring from the time I accelerate from 800 RPM to 1800 RPM and then shutting off. I decided to disconnect the MAF sensor to

identify how she'll run without this sensor. Now, obviously with the MAF disconnected the vehicle would be more sluggish! and that it was. However, when accelerating from the said

800RPM to 1800 RPM this time, the vehicle did not shut off ! And instead of the intermittent rough idling, the idle was now "hunting".

Now, to my basic knowledge, this MAF sensor comprises of a board/ meter that can go faulty after "heated" / on for a long period of time. Therefore, could it be that my MAF needs changing?

I have attached a pic to the further below of my MAF. Please provide me with a reasonable link to this sensor.

LScowboyLS

I think I would just clean the MAF with some CRC MAF cleaner (do NOT touch the sensor with anything other than this spray, such as a cloth or brush or anything!)

To get to the most likely culprits in this case, I still say you have to focus on to the two items that fail so regularly on a 96 model, and these are Idle Air Control Valve and ECU caps! (and "hunting" idle is a symptom of both!) - both were bad in my 96, for example!

Yamae

Sorry to say but that's exactly what I have imagined. But I feel ease that you aren't regretting it nor giving up.

As far as I know hearing from shop owners around here that old Celsiors that couldn't be fixed are often exported as parts or the as-is condition instead of sending them to junkyards. Most of those may have hidden problems. I hope yours is not one of them.

I find many of those have failed ECUs but there are just few owners who want to fix the car using a expensive new ECU which costs more than the value of the car. UCF10 or 11 only values 20,000 Yen / $200 or less here. I have seen a situation that a junkyard ECU was used but it didn't fix the problem then another ECU which has a bit different part number was tried but there started different problems. The owner finally gave up fixing the car.

In Japan where traffic jams and city drivings are daily affairs, a 100,000km is often considered too much. But in some other countries, a 100,000km is still closer to the starting point. The difference of values make it possible to do the business.

LScowboyLS

100,000 km

LS400 owners in USA often get 700,000 km on these cars!

Tuha

Hi Matt, any more progress? Are you winning?

MattLS400

Tuha,
Thanks for your interest. I ordered the CRC MAF Cleaner which the Cowboy recommended, I should have this by Saturday. So thats my project for the day. I just need to find a DIY Manual to clean this MAF. Was wondering if should remove the MAF in its entirety and clean, or simply leave it on, with the engine running and spray this CRC. However, this may be a risk, as all that gunk that would be dissolving from the CRC would feed into my Throttle body which was cleaned 2 months ago.