88 3.2 failed emissions test

[EMJ]

Hi All,
So my 3.2 with 188k on the clock failed emissions due to a high CO %. Don't have the exact number in front of me but I believe it was like a point over. I've done some research and I understand to check the O2 sensor, and ensure it's plugged in, take it for a spirited drive right before the test, and check the basics - plugs, wires, etc. The plugs have 30k on them, the wires, 10k. I'd like to start with checking and/or replacing the O2 sensor. Can someone help with where it's located?

The car has a 2-in 2-out B&B exhaust with headers. Four years ago I replaced the cat converters for it to pass emissions then. The car is due for an oil change as well, and I believe was a little low when the car was tested.

Any help is greatly appreciated. Thanks!

[Drisump]

Mine is located on the drivers side exhaust, follow the wire and it's pretty obvious. Good luck

[shadowjack1]

EMJ:
The O2 sensor is located on the drivers side of the car and screws into the cat. The wire runs thru the tin on the same side. It has a "cylinder" shaped plug. Look below the fuel filter area.

[Targa Me]

Clean out your breather hoses. The oil residue that sits in there can raise your CO levels as well. Also make sure your rear tires are properly inflated, actually over inflated for the test is better, it puts less of a load on your engine.

[EMJ]

Thanks, guys!

[EMJ]

My o2 sensor was replaced about 35k miles ago, now that I'm thinking about it. Would it be common that it would fail so quickly? I perform almost all DIY on the car and haven't disconnected it. Just wondering about that. Hopefully, it's disconnected or the wire is worn, etc.

Any other ideas I could do? I'm doing the suggestions offered and since the oil change is due, I'll take care of it tomorrow, rev up the car for a few miles on a spirited drive, then go in for the second emissions test. Any other tricks of the trade?

[Targa Me]

The life of an O2 sensor depends upon the running condition of the engine. If you engine is poorly tuned or needs some major work the sensor won't last very long.

[86 911 Targa]

Originally Posted by EMJ

My o2 sensor was replaced about 35k miles ago, now that I'm thinking about it. Would it be common that it would fail so quickly? I perform almost all DIY on the car and haven't disconnected it. Just wondering about that. Hopefully, it's disconnected or the wire is worn, etc.

Any other ideas I could do? I'm doing the suggestions offered and since the oil change is due, I'll take care of it tomorrow, rev up the car for a few miles on a spirited drive, then go in for the second emissions test. Any other tricks of the trade?

Prior to smog test, I pull the oil cooler fan relay,
and run the temp up to about 230F.

Here are the results from the most recent test:

[EMJ]

Originally Posted by Targa Me

The life of an O2 sensor depends upon the running condition of the engine. If you engine is poorly tuned or needs some major work the sensor won't last very long.

Thanks, Targa. The car has recent new plug wires, dizzy cap and rotor, but the plugs have about 30k on them. Still, it pulls like crazy to red line and runs smooth at idle. I still have 2 more tries at the emissions. If it fails tomorrow, I'll put in a new 02 sensor, replace the spark plugs, and try again. Thanks for the help!

[Joe Bob]

Take it to a shop and pretest it......they can probably adjust or recommend a fix.

[rusnak]

I might suggest that your aftermarket cats ciuld be bad already.

[Targa Me]

Originally Posted by joe bob

take it to a shop and pretest it......they can probably adjust or recommend a fix.

+1

[KNS]

Unlike newer cars after 30,000 miles spark plugs should be changed. Easy and cheap.

[kidrock]

a fresh oil change does wonders before a smog test. And if nobody has said it yet, make sure the infamous "brown wire" to your DME is plugged in.

[db_cooper]

You will want to change the oil and be sure the engine is at operating temperature
prior to the test. Also temporarily plug the 10 pin connector together too. From Steve Wong's website.

[EMJ]

Great tips! Thanks!

BTW, gratuitous bad IPhone picture of the old girl... Seven years, I still look back every time I leave her in a parking lot...

[stlrj]

"So my 3.2 with 188k on the clock failed emissions due to a high CO %."

That is usually an indication of a rich running condition. Why not have the mixture adjusted? The air flow meter does have a CO adjustment screw as well as adjustments that can be made under the AFM cover that would easily lower CO.

Also, your 02 sensor would last much longer with the CO set to correct factory spec.

[Brando]

Any update? Pass?

When I had this issue last year I went the new route... Borrowed a NIB Catalytic Converter and installed a new O2 sensor. Did a valve adjust/oil change and passed with flying colors (after 3 failures).

[EMJ]

Originally Posted by stlrj

"So my 3.2 with 188k on the clock failed emissions due to a high CO %."

That is usually an indication of a rich running condition. Why not have the mixture adjusted? The air flow meter does have a CO adjustment screw as well as adjustments that can be made under the AFM cover that would easily lower CO.

Also, your 02 sensor would last much longer with the CO set to correct factory spec.

Stirj, You're spot on. The car does run a bit rich. I'm trying to fix this issue tomorrow myself as I won't have time to take it to the shop until next weekend. I've found the AFM adjustments can be a bit tricky and best left to my mechanic. For tomorrow's test I'll:

- Connect the brown wire on the DME (If not already connected)
- Change the oil
- Check the O2 sensor
- Take a "spirited" drive right before the test
- Keep the car at operating temperature right up until the test

If it fails:

- Change the 02 sensor
- Adjust the mixture at the AFM (Mechanic)

Retest...

Did I miss anything?

[darrin]

you do have the ability to make reversible changes to the mixture using the rotary knob on the underseat dme unit. See Bill Underwood's Porsche 944 World - Tuneup Info for 924 - 944 and 951 Porsches for details (on the 944 box -- I believe the 911 has the same criteria) -- you could use the option that leans out the engine by 3% without affecting the timing and see if that gets you past your slightly too rich condition for emissions purposes and then set it back to where it was (confirm it's at Position 1 before you start tweaking) once you pass emissions. This is nice as it's reversible