85 Carrera...Won't pass SMOG!!!

[PcarRacr]

Anyone else had this problem? I have a high milage 911(157K) and this car has always passed smog but a few months ago it didn't even come close so I started chasing problems and changing things to try and make it pass but so far I have had no luck. Below are my results from today. As you can see the CO% is off the charts.

Went for the test and was feeling good because so far I have changed the ISV(IAC motor), Head Temp Sensor, Put a Stock Chip in it and the car has an O2 sensor that is only a year old. So I find out today that the car is worse than before!....the sad thing is that the car runs great...smooth as silk.

Here's the results.

The Problem lies in these two areas:

CO% I scored a 7.91 and the max allowed is .85

HC I scored 177 with a max allowed of 138.

The car was great in NO, %CO2(so the cat is working good), %O2.


So as you can see its C0% is still off the chart. Before I made these changes it was at 5.91 which is still way high and the HC were measured the same as above.

Does anyone have any ideas? Is the 02 Sensor junk?

This car has spent the last 3 years of its life exclusively on the track but now that I have a new "race car" I want to put this one back on the street. I figured since the motor is stock and so is the exhaust I didn't figure I would run into soo many problems.


Thanks Again,
Chad Armstrong
85 911 V4 POC #192

[Wayne 962]

Clarify your numbers please - can't read them in your post...

-Wayne

[PcarRacr]

changes the layout of the results

[scottb]

Take to TRE. Dave and the boys will sort it out.

[Wayne 962]

Typically when your CO is way high, that means you're running too rich. Richness of the mixture should be monitored by the oxygen sensor. I would check all the O2 sensor connections, and maybe replace the sensor again. Something indeed is wrong with that circuit...

-Wayne

[stlrj]

How can it go rich if it is adjusted correctly to spec: CO... 0.6-1.0*

How could it be an 02 sensor issue if the correct mixture is set with the 02 sensor disconnected and set at a fairly lean default setting to begin with?

[dvkk]

During the last 3 years on the track were you using race gas? If so, some of it has lead which will kill your O2 sensor and your Cat.
Your engine is running rich, and your Cat is dead.

[PcarRacr]

During the last 3 years of tracking the car I only used 91 octane. No leaded race gas ever. Plus the cat has been off the car for the whole time so It shoudl be fine. It only have 200 miles on it with the cat maybe.

As far as the O2 sensor goes...the connection to the O2 sensor borke a while back....well the plastic clip broke so the two wires can flot free...I am wondering if they are plugged in backwards because without the clip you can plug the two wires in anyway you want. I just don't know how to test if the O2 senor is working or not.


Chad

[cowtown]

Instead of trying to test this disposable part, considering you are spending $70 for every smog check you fail, I'd get a $40 sensor for a Ford Mustang and put it in. It is a Bosch part and works just great in the Carreras. My '88 Just passed in CA (Smog2) with one of these sensors. Just make sure you do very good solder connections and use heatshrink.

Sensor should output 0-1 volts. It should have 3 wires, two white, one black. Black is signal to ground, the two whites get 12V and ground for the heater element and are reversible. Test for 12V to the heater also.

You can try to get some carbon out of the engine by misting water in the intake at high idle.
One last thing you might try is plugging back together two wires at the wire harness at the DME if they are unplugged. This leans out slightly for CA cars. But I doubt it will fix a 7% CO situation.

I agree with you that your cat may be OK, given that NOX is in spec.

Good luck!

[PcarRacr]

I have extra Bosch Ford Mustang O2 sensors as well As the O2 Sensor that I took out of the car a year ago(its probably still good) so I have plenty to try.

Again thatnks for everyones input and I will let you know how it goes.


Chad

[cowtown]

Just one last thought - with that kind of richness, maybe a leaky injector could be at work?

[Lorenfb]

The CO should be about 1.5% or less before the CAT w/o the O2
sensor. Disconnect the O2 sensor and troubleshoot your problem
without it. A good O2 sensor really can't "deal" with a 7% CO level,
so don't waste your money on an O2 sensor yet as some have
suggested. Also, leave the stock chip in until you fix the problem
and pass the emissions test.

You need to do some basic checking:

1. the fuel pressure
2. the head temp sensor
3. the air flow meter (Make sure it hasn't been mis-adjusted.)
4. the O2 sensor input to the DME (pin 24) isn't grounded
5. WOT switch input to the DME, pin 3, isn't grounded

Also, check out this web site (www.systemsc.com) on the Diagnostics
page (Poor Running) for some additional info.

[john70t]

Loren way-more-than posted what I was going to say.
The O2 sensor is used for fine-tuning, and even a good cat is only good for a couple percent CO and a couple hundred HCs, so this is something major. You see low NOX because a rich mixture is running cool(and dirty).
If all of the above check good, the only thing left would be a couple bad plugs sending raw gas downstream, but that should make it run poorly.