98 a4, 215,000 km's, apr chip and intake. Failed emissions test idle part only, co% was 2.90 limit is .70. The rev test ( cause no one has a foul wheel dyno) passed by a mile. Could the reason I failed the idle test be because of my cat or o2 sensor? Is ther any way to tell if my cat is done? Or my o2 sensor? I have no CEL nor have had one recently. The car doesn't get out much, however I drove it for 3 days before the test. I also got the engine hot before the test . Any input would be very helpful. Thanks

 

You're probably running rich. Was the car hot when you had it tested?

 

Okay, best advice I got, Don't wear short skirts in dark alleys.

Try running sea foam through the gas to help clean everything up. Scan for codes stored. If your cat or O2 sensor were done you'd have a cel.

 

Since it's only at idle, and not while revving, I'm gonna throw in the idea of EGR issues (EGR shuts down when the throttle opens - it's only functional at idle). That's a distinct possibility. You said it's a 98 but didn't mention what engine, although since you bought a chip I'll assume it's a 1.8T. You'll have EGR lines that lead back to the throttle body so that the gases can be recirculated and re-burned. If that's clogged or really dirty, I can see it causing your problems. I'd clean the system out manually as well as running a seafoam treatment like Jiggleo suggested - do the vacuum system treatment on it (search feature will find tons of info on this), and then try again.

 

I live in Canada, my car does not have an EGR its a 1.8t aeb engine. What else could it be?