My 99 GSR is failing Colorado emissions, here are the details.

Car is tuned on a VAFC - relatively stock car, ITR catback, DC header, ITR pistons, LS crank

Everything else is stock. Here are the results with the first go-round:

HC Readings : Allowed : 1.2 - Emitted: 1.7
CO Readings : Allowed : 15 - Emitted: 34

After this reading, the oil was changed, seafoam was run through the car, changed the plugs (after the seafoam) and car was run hard on the way to re-test (next day) to warm up the cats

Here are the readings this time:

HC Readings : Allowed : 1.2 - Emitted : 3.4
CO Readings: Allowed : 15 - Emitted : 55

Is it possible that when the seafoam was run through the car, the O2 sensor was fouled causing higher readings?

Any help is much appreciated!

 

Anybody with any ideas?

 

For the most part, I would turn the VAFC off and just run the stock fuel map unchanged. Then go ahead and switch out the O2 to see if that is the case. Your build seem normal. The DC header at times tends to take out the O2 because of the change in air.

These are just some opinions from what I can see, Im not an expert ...

I ran my car to the smog place with my tuned ecu that was rich with fuel and when I got there, I put on the stock ecu. I was high on CO I believe but I still passed... The only reason I could be that high is because the car was barely switched over and had the fuel in the system still...

Good luck...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Dang EG &raquo;</TD></TR><TR><TD CLASS="quote">For the most part, I would turn the VAFC off and just run the stock fuel map unchanged. Then go ahead and switch out the O2 to see if that is the case. Your build seem normal. The DC header at times tends to take out the O2 because of the change in air.

These are just some opinions from what I can see, Im not an expert ...

I ran my car to the smog place with my tuned ecu that was rich with fuel and when I got there, I put on the stock ecu. I was high on CO I believe but I still passed... The only reason I could be that high is because the car was barely switched over and had the fuel in the system still...

Good luck...</TD></TR></TABLE>

Thanks for the response.

I'm going to have the car re-tuned tomorrow and possibly change the O2 sensor. Hopefully that'll do it.

Thanks again.

 

Bump for more insight.

 

You might retard the timing 2deg, and how old is the cat? You might put a new
cat and o2 and it should pass. How many miles are on the motor?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rd91sib18c5r &raquo;</TD></TR><TR><TD CLASS="quote">You might retard the timing 2deg, and how old is the cat? You might put a new
cat and o2 and it should pass. How many miles are on the motor?</TD></TR></TABLE>

Only 90,000.

I think I may just have it retuned and change the O2 and cat and see what happens. Thanks guys.

 

High CO means the car is running too rich...
If it runs rich enough, you will have incomplete combustion(misfire) and HC will go up...

Solution- Lean out the areas where your being tested in to bring both of those numbers down...
If your engine is near stock, you should just zero everything out and let the stock fuel maps do their thing...