Need help passing emissions

Ron Egan · 05-13-2004, 09:16 AM

I recently had my '85 Carerra emissions tested and failed due to high CO and HC readings. The car was tested last year and passed with no problem whatsoever.

Since last year, I have added a Euro pre-muffler, dual exhaust and one of Steve W's chips (I did not realize that his chip did not make use of the O2 sensor until I spoke with him a few days ago...). I replaced the chip with the stock chip, replaced the Euro pre-muffler with the cat and still can not pass the test.

I have a new O2 sensor and plan to install new spark plugs before having it re-tested and was wondering inf anybody had any additional suggestions.

Additionally, the car has not been used much in the last year (<250 miles). I was also told that I should run the car hard for a period of time before getting it re-tested so that the cat is up to operating temperature. It was also suggested that I add a couple of bottles of fuel line anti-freeze as the alcohol content will make the car run a little leaner.

Any additional suggestions would be appreciated.

Thanks,

Ron

1985 911 Carrera

AZ1977911 · 05-13-2004, 09:28 AM

Make sure your running HOT when testing. Have your CO set to 2% or a less before testing.

bigrubberjeep · 05-13-2004, 09:33 AM

Check the sensor on the cat as well, it may be bad

Ron Egan · 05-17-2004, 03:58 AM

Well, I changed my O2 sensor, added some fresh fuel and drove the car 40 miles before having it retested. It failed again !!! My CO reading dropped from 3.96 to 3.22.

What else can I try ? I am really at a loss as to what the problem could be. The only thing that I have not done is change back to my original muffler (I went from the stock single outlet to a RUF dual exhaust).

Any suggestions would be greatly appreciated.

Thanks,

Ron

Lorenfb · 07:25 AM

Your car should easily pass an emissions test. The CAT has the most effect on
NOx and not the CO & HC.

You need to check:

1. the temp sensor
2. the fuel pressure
3. proper operation of the O2 sensor
4. the air flow meter ( no one has misadjusted it)
5. DME switch settings a "1"

The readings before CAT (unconnected O2) should be 1.0 to 1.5% CO.
Once the O2 is hooked up, the CO should drop to less .5% after the CAT.

Check out this web site (www.systemsc.com) on the Diagnostics and Problems
pages.

Note: Isn't interesting what we learn about what chips really do!

"Since last year, I have added a Euro pre-muffler, dual exhaust and one of Steve W's chips (I did not realize that his chip did not make use of the O2 sensor until I spoke with him a few days ago...)."

Ron Egan · 05-17-2004, 07:30 AM

Problem resolved....the shop I took it took said their was an issue with the wiring on the O2 sensor (it was not shielded properly). This was repaired and it passed with no problem.

cowtown · 05-17-2004, 07:40 AM

Quote:

Originally posted by Lorenfb
Note: Isn't interesting what we learn about what chips really do!

Quote:

Originally posted by Ron Egan
Problem resolved....the shop I took it took said their was an issue with the wiring on the O2 sensor (it was not shielded properly). This was repaired and it passed with no problem.

No Ron, it must have been the CHIP! Even though you went back to the stock chip for the test, it was the chip! The chip!!!

Check out this web site (www.dohwrongagain.com) on the Diagnostics and Problems
pages.

bigrubberjeep · 05-17-2004, 07:54 AM

Congrats!

Steve W · Steve W's Garage

Quote:

Originally posted by Lorenfb

Note: Isn't interesting what we learn about what chips really do!

That sir has been only on certain versions of the chips used for the 84-86 Carreras and all European 930/20 versions. All other versions, including the 87 to 89s all utilize the O2 sensor.

But then I am not surprised to hear this comment from you, especially from someone who has been trying to peddle his own performance chip for the 3.2 Carrera all these years without any success. Too bad I have been told, and I quote "they don't do jack". No wonder you think everyone else is just feelin it in their head.

Lorenfb · 05-17-2004, 04:32 PM

"Well, I changed my O2 sensor, added some fresh fuel and drove the car 40 miles before having it retested. It failed again !!! My CO reading dropped from 3.96 to 3.22."

A properly running 3.2 shouldn't have these high CO numbers even with the O2
disconnected. Your car is probably running near the O2's limit to regulate the
AFR to the emissions optimum of 14.7. Your car probably needs to be checked
further for other potential problems.