Sniff test gone bad...
 

Darn. My car failed the VA sniff test, twice. I need suggestions from my esteemed Dorki brethren on what to do next.

On Saturday it failed all three: HC, CO%, & NOx. So I slapped the Catalyst on and went back this AM. Now, of course, it only fails for HC and CO% -- NOx is near zero.

CO% is about 2.3% at the test load, testing limit is .8% (or so).

HC limit is 135, my car was just barely over at 138.

My car passed two years ago without the Catalyst and the only change made since then is a Steve Wong chip.

One other bit of info is that the car developed an intake whistle under very small throttle openings about a year ago... I haven't been able to isolate the cause, so there is a chance it is a small vacuum leak.

So my questions are... keep in mind that I am tired of waiting in line just to fail emissions & would really like to be sure the car will pass before I try again.

1) Can I fix this at home? And what special tools would I need (e.g. gas tester)? Can this be fixed without changing the DME chip or is that the primary problem? Could the suspected vacuum leak be responsible?

2) Would I better off just taking the car to a shop? If so, what shops are good for emissions tuning?

Thanks, guys & gals, for the help!

I think part of this is because you may be running too rich for the cat to do it's job. Here is a chart. On the rich side, both HC and CO are high.

This does not show the NOx but when running too lean the NOx rises. Because of the unused O2. When rich all the O2 is used and you have left over fuel not being burnt thus it is high.

It might be as simple as putting the stock chip back in.

Can someone confirm?
If I'm wrong, at least you have the chart for reference!

http://www.dorkiphus.com/porsche/mod...hart_sized.jpg

Have you put the OEM chip back in?

John:

I'd recommend:

1. OEM chip
2. Change the oil and filter (high HC content)
3. run with cat on
4. use propane / carb cleaner to test for air / vacuum leaks

Change the oil and filter on every car I have to run through emissions and they pass (even with aftermarket chip, etc...). Your motronic in the Carerra doesn't like air leaks downstream of the air flow meter. Engine will run lean, O2 reports back lean mixture and then FI richens up ... yadda, yadda... Look for air leaks downstream of the AFM, especially around the intake runner / plenum gasket to heads.

Jase

Thanks guys for the responses so far. Very good suggestions. Bill, that graph is extremely helpful... looks like my car is running @ about 13.5:1 given the CO%.

Anyone have an OEM chip I can borrow?

I only have the Wong chip and the Autothority one that came with the car -- I could try the Autothority, but it is probably bit rich, too.

Isn't there a selector switch on the DME that leans things out a little? I seem to remember reading about it somewhere but can't remember where.

Think I'll send an email to Steve Wong and see what he suggests.

Yes dump the chip for now. At idle measuring gasses before cat, O2 sensor unplugged, you should get .6% CO. HC typically will be about 10-20PPM dependent on mileage. (CO2 will be 8% or more and O2, 2-4%) With O2 sensor connected and reading at same test point, CO will drop to .22. HC will drop a little more. At end of tailpipe CO will drop to 0. HC will drop to 0.
If this not the case deactivate idle system at plug on elect board; reset idle and CO to desired values. If there is a manifold leak, the O2 values will be high (measuring before cat and O2 sensor unplugged).

Here's a thread I started on Pelican about getting my 930 to pass. While tuning a CIS 930 to pass emissions isn't directly applicable, there may be some tips that you could use. There's a lot of technical discussion in there.

http://forums.pelicanparts.com/showt...p;pagenumber=1

In the end, you'll see that mine passed w/ cat, w/o air pump, w/o oxygen sensor, w/ judicious use of the mixture screw.

John, I've got the stock chip from my 88 Carrera in my tool box. You are welcome to borrow if it will match. I got mine through sans cat with the Autothority chip. Leak sounds likely culprit.

Bill W.

John ~

As another data point my 84 Carrera passed with no cat (Fabiani by-pass) and the Steve Wong chip. It was close and I would have to dig up the results but it passed on the dyno. Steve has redone my chip many times to keep up with my mods so it is on the bleeding edge of performance with no detonation.

I remember when I was stock with the cat and a dyno test in MD the car barely even registered anything, it was that clean.

If your objective is to get the car passed that is one thing, but there is definitely an issue with your mixture if you cannot pass with a cat.

I would track that down first and passing will come as a result of your efforts. Make sure those intake gaskets are not inducing a rich condition. Carb cleaner while running (don't try this at home folks) will make the idle jump...

-Jeff

John

I don't know if this will help, but from time to time I have to send my clients cars through MD Emissions. One of the things that I have my Q/C testers do especially if there is a line of cars waiting is keep the idle speed up so that when the car goes through the line the cats are nice and hot. Helps every time!!

Mike