O2 sensor plug?

brendon · brendon's Garage

Can anyone tell me if the thread pitch for an O2 sensor is universal, or at least if the one used on an 80SC is 18mmx1.5?

I want to remove the sensor and just plug the fitting (running with O2 unplugged anyway) - all the plugs I can find are for 18mm x 1.5 thread pitch.

Thanks

Zeke · 11-01-2006, 06:54 PM

Why do you not use the o2 sensor?

BTW, if you're gonna plug it, don't worry about the pitch. If it's close, it will plug it.

brendon · brendon's Garage

The car doesn't run well when it is plugged in, so I run it unplugged. May have something to do with it only reading one bank (SSI's)

I would like to get the correct size plug for the fitting as I don't want anything crossthreaded making it not reversible.

scarceller · scarceller's Garage

Quote:

Originally posted by brendon
The car doesn't run well when it is plugged in, so I run it unplugged. May have something to do with it only reading one bank (SSI's)

I would like to get the correct size plug for the fitting as I don't want anything crossthreaded making it not reversible.

Very interesting, I just posted a question about this issue with SSIs only having O2 on the left side. I to have SSIs 2in2out muffler and see rough idle when I plug O2 sensor in. It seems that with the O2 sensor plugged in the DME brings my CO at the tail pipe (NO CAT here) to .5% and it runs rough at idle. But if I disconnect the O2 sensor and adjust the CO to .8% via the Air Bypass screw on the AFM the idle clears up.

I really think this design of only having the O2 in the exhaust stream of 3 cyliders is a bad idea.

If I have sometime in the future I plan to install another O2 on the right side SSI then with both inplugged see what they read. Looking for left to right bank unbalanced condition.

Nice to see smeone else suspects this as well.

fastpat · 11-02-2006, 07:42 AM

Quote:

Originally posted by scarceller
Very interesting, I just posted a question about this issue with SSIs only having O2 on the left side. I to have SSIs 2in2out muffler and see rough idle when I plug O2 sensor in. It seems that with the O2 sensor plugged in the DME brings my CO at the tail pipe (NO CAT here) to .5% and it runs rough at idle. But if I disconnect the O2 sensor and adjust the CO to .8% via the Air Bypass screw on the AFM the idle clears up.

I really think this design of only having the O2 in the exhaust stream of 3 cyliders is a bad idea.

If I have sometime in the future I plan to install another O2 on the right side SSI then with both inplugged see what they read. Looking for left to right bank unbalanced condition.

Nice to see smeone else suspects this as well.

You could replace the fuel control on your SC with Megasquirt EFI and run two O2 sensors on the system, and have a whole bunch of additional benefits.

brendon · brendon's Garage

Quote:

Originally posted by scarceller
Nice to see smeone else suspects this as well. [/B]

My mechanic was looking it over because I got tired of chasing my poor running issues and determined disconnecting it was my best option, since i don't run the cat either (obviously, since I mentioned the SSI's).

I may just bite the bullet and buy the plug from Summit and see if it fits - it's only about $10.

DW SD · 11-02-2006, 01:47 PM

A plug should fit. I think it is 14mm x 1.5 or 1.0 pitch thread. their O2 sensors will be compatible. The thread is (pretty much) universal.

brendon · brendon's Garage

It just hit me...why not check out the local parts store. As I was brousing the isles I ended up in the oil change section and found a replacement drain plug - size 18mm X 1.5 - perfect fit and only $3

quattrorunner · quattrorunner's Garage

Why would it matter that it only has one o2 sensor? It isn't efi, so it's not going to adjust electronicaly from side to side. If the car isn't running in the O2 paramiters, it will be the same on both sides.

scarceller · scarceller's Garage

Quote:

Originally posted by quattrorunner
Why would it matter that it only has one o2 sensor? It isn't efi, so it's not going to adjust electronicaly from side to side. If the car isn't running in the O2 paramiters, it will be the same on both sides.

This is true, but lets say for some reason the right side was rich and the left lean. With only one O2 on the left the DME does not average the 2 sides and the result is the DME only reading the O2 on lean left side and making the overall mixture richer, this solves the AirFuelRatio on the left side but only drives the right side richer. However, if the DME had average numbers by having the O2 sensor read combined exhaust from all cylinders the end result would be to do nothing and leave the mixture alone.

Let me explain by numbers:

Assume O2 sensor sees exhaust from all cylinders: If we assume the left side is lean say 15/1 AFR and the right was 13/1 AFR then the average would be 14/1 AFR and the DME would leave the mixture alone.

Take this same condition with O2 sensor only on the left side, then the DME sees the left side lean at 15/1 and drives it richer to 14/1 but the right side was originally at 13/1 so it now was driven further rich to 12/1. What has just happened is that you made a inbalance condition even worse and you actually messed up the average, remember the average was 14/1 but now as a result of O2 only on the left side the average AFR was driven to 13/1. Your emmisions test has just failed!

As you can see, the worse the inbalance the worse this problem becomes.

Of course this would not be an issue on a motor that has left and right side perfectly balanced (NO AIR Leaks). I guess I just would feel better if the O2 sensor saw the flow from all cylinders and not just 3. But I really would prefer 2 sensors one on the left side and one on the right. If we had 2 we could quickly look for left right mixture diffrences by just putting DigitalVoltMeters on the sensors (Disconnected Sensors), you would see very quickly if they are both at Lambda (about .5v on the meter).

I started thinking about this because my idle goes bad once I plug my O2 sensor into the DME. I have SSIs with 2in2out muffler. I suspect my right side is running rich by the looks of my spark plugs. I'm really thinking about putting another O2 sensor on the right side just to verify Lambda between the 2 sides. I would then remove the O2 sensor from the right side and install a plug after testing.

Basically I would love AFR meters on both SSIs just to see that they are balanced.

When working on an unknown motor anything could be causing AFR inbalance from left to right side. Here are a few things:
1. Cam timming slightly off left to right
2. Air Leaks on one side
3. Bad Compression / Leak down on one side
4. Bad spark plug / wires
5. Bad injector
I'm sure folks can think of a few more.

quattrorunner · quattrorunner's Garage

The cis doesn't controll both sides seperatly.

Zeke · 11-03-2006, 08:08 AM

I checked the threads. Definately 1.5 pitch.

84toy · 11-03-2006, 08:14 AM

Maybe a dumb question but have you tried replacing the sensor? I run several vehicles with one sensor on one side with no problems.

glenncof · 11-03-2006, 08:16 AM

My O2 was Bosch on 1985. Go to www.BoschUSA.com or other manufacture and find a spec sheet on the sensor to get thread info.

I have even found mechanical spec's from Bosch on my 20+ year old seat motors when I punched in the Bosch p/n.

scarceller · scarceller's Garage

Quote:

Originally posted by 84toy
Maybe a dumb question but have you tried replacing the sensor? I run several vehicles with one sensor on one side with no problems.

Sensor is new.

glenncof · 11-03-2006, 10:17 AM

scarceller, See diagrams at Bosch for pre/post Cat numbers

http://www.boschautoparts.com/NR/rdonlyres/FACC2165-104B-45FE-BADE-960DF4C5B066/0/emissions.jpg

The O2 is a trim. I did not replace the one on my 1985 until about 160K miles. Life expectancy for mine is 60K miles. I was passing all California Smog testing every two years. Of course I have a Cat. Convertor on it. The reason I replaced is Cal. is now doing dyno smog testing and didn't want to fail.

Therefore I conclude the vehicle should run without problem if everything else is OK. Sensing on only one side should not be an issue assuming you're balanced.

O2 sensor could be contaminated but since it's only a trim I would not expect it to cause drivablity issues by itself. See the Technical Resource section on the above bosch site for pix.

76carrera3.0 · 11-03-2006, 11:02 AM

Had a plug at my desk at work measures at 18mmX 1.5 pitch, threads into my ssi's no problem.

brendon · brendon's Garage

My snesor was new last spring so only about 1500 miles on it before I disconnected it. The car runs much btter without it; and without a cat, don't really need it. Mixture is set good and car drives good.

And yes 18 x 1.5 is correct
It's a $3 oil drain plug from the corner parts store.