92 MTX 3.2l is eating 02 sensors?? Wiring Harness Issue!!

[vortex2450]

Hey, I swapped in a 3.2l little more than a month ago, when I did the swap I replaced both upstream 02 sensors, 3 weeks after that my gas mileage was lacking, so I pulled both sensors and the rear sensor rattled when I lightly shook it... So that's o2 sensor #2 for the rear bank after the swap. NOw i'm throwing the 172 code again I the car seems to lack some power so I suspect the rear sensor went AGAIN! At $40 a pop these aren't cheap.... I haven't checked it out yet but what could be doing this?

Also, it's notable the before the swap the rear 02 sensor on the car failed and threw a 172..... It also rattled...

I don't know, I suspect since it's a different engine maybe my wiring is ***** and somehow physically breaking the sensors?

Or maybe my y-pipe is at fault?? It's not a 3rd part pipe but looks custom welded, the rear outlet isn't equal length, it just comes straight down about 8" thens hits a shallow 90 degree bend into the collector... the 02 sensor bung is about 3-1/2" from the exhaust manifold...

I'm slightly irritated because I know i'm loosing mileage and power but I don't wanna fork out another $40 for a sensor before I fix the issue...

-Josh

Also, if it helps, the engine makes a little noise in the valvetrain, it seems to comes from the rear bank, this may be a related or not, but at least I could mention it

 

[sperold]

The manual transmission cars use a 3 wire, heated, O2 sensor (I think) and the automatic cars use a 2 wire, O2 sensor.
The sensors are different.
Don't know if that helps your situation.

 

[SHOracer14]

Acoording to my sources the O2 part number is the same whether ATX or MTX. I don't see a need for a heated O2 as they are both fairly close to the engine and there are no "down-stream" O2's on gen 1/2 cars.

 

[32MTX]

I don't think the o2 is heated, I could be wrong

usually those are 4 wires and on 96+ cars

sounds like you could have another problem throwing that code, what is the code definition? is it a lean or rich code? this could be a fuel/air issue/leak somewhere after the MAF and before the o2 sensor.

 

[SVOFANATIC]

2 wire isn't heated, 3 wire is but the heater is grounded through the pipe, 4 wire is also heated but the heater is grounded through the 4th wire.

 

[32MTX]

what kind of sensors are you buying? brand/store?

o2 sensors are the one thing I've never messed with on my car except unplugging them for y pipe removal..... I think they are 170k+ mile originals....

 

[vortex2450]

I don't think the o2 is heated, I could be wrong

usually those are 4 wires and on 96+ cars

sounds like you could have another problem throwing that code, what is the code definition? is it a lean or rich code? this could be a fuel/air issue/leak somewhere after the MAF and before the o2 sensor.

All the sensors I've used are three wire sensors, and if I turn the key on the get hot on their own. SO i guess mine are heated.

I'm positive this is an o2 sensor problem, I pulled the sensor today and it was broken just like the new one before it and the one before that. A rattle is the result light shake. Plus I'm getting crappy MPG and the car is at a slight loss of power, it's the o2 sensor being sabotaged..

what kind of sensors are you buying? brand/store?

o2 sensors are the one thing I've never messed with on my car except unplugging them for y pipe removal..... I think they are 170k+ mile originals....

Both sensors I bought were Bosch part # 13492. The sensor before that I can't be sure of what brand it was, I bought the first bosch off RA and the second from Advance Auto..

The other 02 that came from RA is just fine, no problems with it, I'm beginning to think the bung location may be the issue, the car has a cat-less y-pipe ...

I snapped some picture of the how far the bungs were from the dumps of the exhaust manifolds..

The first one is the rear which is were the 02 sensors keep dying...




The second picture is the front which seems to be the same distance away as the front...




I'm leaning further and further towards the y-pipe being the issue, unless there is a problem in the wiring somehow creating enough of an issue to cause the internals of the sensor to break into pieces...

I do know if I change y-pipe I'll loose some of the unique sound of my current exhaust set up boasts but I need a functional car, this is the only code I have left, 172, check it twice, 111, 111, then a 172.. I'm tired of my SHO feeling sluggish and running rich burning gas, it's getting lame..


-Josh

 

[kevinspann]

I'm not sure if that's your issue - on the aftermarket y-pipe I have in the garage, those distances are about 2" for the front, and 3" for the rear (bottom of ****** to top of 02)

 

[vortex2450]

I'm not sure if that's your issue - on the aftermarket y-pipe I have in the garage, those distances are about 2" for the front, and 3" for the rear (bottom of ****** to top of 02)

Here the distance is 2-1/2" for both sensors, whatever the issue is it's happened on both engines, and always to the rear plug. I cease to understand it..

the actual measuring element inside is ceramic is it? I'm thinking I'm going to try and use a 2 wire non heated sensor and see it lasts.. Maybe it's simply getting too hot and cracking and being blown into peices? Unless anyone else has any ideas...

 

[rubydist]

mtx v6 cars use a 3-wire o2 sensor.
atx v6 cars use a 4-wire o2 sensor.

I would try a different brand of o2 sensor.

 

[vortex2450]

mtx v6 cars use a 3-wire o2 sensor.
atx v6 cars use a 4-wire o2 sensor.

I would try a different brand of o2 sensor.

Wilco, but why would the front bank be a ok and the rear bank constantly breaking? Well I'm going with either the Denso or Motorcraft sensor next..


-Josh

 

[vortex2450]

I swapped in an NTK brand sensor for the rear bank and I didn't drive 2 miles down the road before the CE light popped back on (yes I cleared the codes). I haven't looked under yet but obviously something is wrong..

I'm loosing patience here, considering wiring an inline resistor to simulate an approximate normal voltage until this can be figured out.

-Josh

 

[kevinspann]

Is the y-pipe seated on the manifold completely? You don't have a leak there, do you?

 

[vortex2450]

Is the y-pipe seated on the manifold completely? You don't have a leak there, do you?

Yes, I made double sure and use exhaust sealant, I have a slight leak at the donut gasket but it's miniscule.

Any train of thought on possible causes here? I'm perplexed. I looked at my ATX y-pipes and they place the sensors in the same region as they are on my y-pipe so I don't believe the location of the bung should be the issue.

-Josh

 

[zak]

Josh, does your Y pipe connect up to the hanger on the oil pan? Some aftermakret ones don't and those will vibrate more.

Maybe you have the heater and signal wires switched. Did you use an MTX harnes or an ATX harness?

 

[vortex2450]

Josh, does your Y pipe connect up to the hanger on the oil pan? Some aftermakret ones don't and those will vibrate more.

Maybe you have the heater and signal wires switched. Did you use an MTX harnes or an ATX harness?

No it doesn't, it is also notable that the bend for the rear exhaust manifold is only 2-3/4"" from the 02 sensor and the bend is a rapid 90 degree curve with a radius of ~ 3" The front sensor is golden and the front bends are very shallow and flowing. I would consider welding a mounting tab on but this y-pipe appears homemade and I believe back pressure is building at the rear bend and creating enough back pressure to **** the sensor.. So it would be a waste of time IMHO.

So I'm planning for a SHOshop y-pipe in the near future.

For now I said screw it, I cut the connector off the rear sensor and spliced the signal wires into the front sensors and so the front sensor will be giving the readout for both banks until I can come up with the money to buy a decent y-pipe. It can't afford 22-23 mpg when my daily commute is 32 miles at the minimum.

Anyone have anything against my temporary fix? I am going to drive it now and see what's what..

-Josh

 

[zak]

Check the wiring per above. If you put 12 volts to the actual sensor by mistake it will fry it and it could break up pretty easily, causing the rattle.

The agressiveness of the bend will not effect the sensor. However, you could have a clogged cat, see if its glowing under normal use.

 

[vortex2450]

Check the wiring per above. If you put 12 volts to the actual sensor by mistake it will fry it and it could break up pretty easily, causing the rattle.

The aggressiveness of the bend will not effect the sensor. However, you could have a clogged cat, see if its glowing under normal use.

The sensors have been breaking since before the engine swap, and after I used the MTX harness. The harness was intact and the only altercation done to it was bypassing the 12v key on feed wire for the injector from the CCRM (I don't remember the pin #).

I haven't checked the rear connector honestly, I did check the front when I spliced into the front sensor though.. the connector from the harness, the two signal input give no voltage readout as they should, just the 12v heater wire as it should. I'm going to go check the rear connector now so I don't fry the front sensor if the connector IS the issue.

The Y-pipe is catless so that couldn't be an issue, I also inspected and blew through it with an air hose a couple days ago to be safe.. If the y-pipe isn't the issue then why would only the rear sensors be the ones going out? I'm beating my head against a wall now....

Thanks,
Josh

EDIT: checked rear connector, it's fine. I'm still leaning towards the y-pipe being my problem at this point, I say this simply from a process of elimination standpoint..

- Tested Connectors - OK
- tried 3 brand new sensors, from 2 company - OK
- no exhaust leaks @ manifold - OK
- Catalytic convertors don't' exist - OK
- Front sensors is fine - ok
- front y-pipe is less restrictive - ok

see where I'm coming from??

 

[sperold]

They used to be an oddity, but now most places have heat measuring guns.
Take your car to a place that has them and have them shoot the temperatures of both pipes near the bung.
With a catted car, they are looking for both ends of the cats to be around 600 degrees F.
If there is a big difference in temperature (due to raw gas being dumped in), then you might have the problem solved by fixing that situation.

 

[vortex2450]

Update: After my ghetto splice the front sensor went, I'm positive I used the right wires so now my attention turns to the wiring harness.

The issues is clearly in the wiring to the connector.

I'm done fvcking around with this, I am going to run all new wires from the connector back to god knows where the need to go.

There is where I need help, where do the wires for the 02 sensor signal go? Can anyone pm me a schematic perhaps?

I know I had the y-pipe as the faulty part here but now it's obvious this is a wiring issue...


I need my car running so any and all help is much appreciated..

-Josh

EDIT: Search rewarded me the PCM pin out diagram.

Checked both connectors.

No continuity both Pin 29 and r/bk wire from connector, all other wires check out including ground.
I believe it's corroded somewhere and it shorting which just fries the sensors @ key on.

Going to run a fresh wire from the PCM and bypass the entire length of the harness to the connector.

When will my luck with this car every turn??

-Josh