My son has a 94 firebird trans am (LT1). It passed smog 4 years ago and 2 years ago. This year the smog guy said the cold air filter did not have a CARB sticker, so i loaned him my K&N cold air filter from my 95 camaro that has a CARB sticker. This should make no difference.
He failed HC. the numbers:

----------RPM--CO2--O2------HC-----------CO-----------NO
---------------------------MAX-MEAS---MAX-MEAS---MAX-MEAS
15 MPH-1322-14.5-0.9---83---98-----.48---.29-----689--481
25 MPH-1517-14.5-0.9---48---65-----.46---.32-----706--629

my son said the guy said maybe there is a leak in an air hose. Are there any obvious things for me to try?

Thanks.

 

What mods does his car have? If the smog guy is whining about the CAI, I would find someone else. I know a guy out here in the SFV that will test you with any mods, as long as all the smog gear is still on (including LTs).

High HC means there is unburnt fuel in the exhaust, so it's running rich. Could be from a slight misfire, exhaust leak, leaky injector, etc.

 

With all 3 contaminants - HC, CO, and NOx high, it may be the cat failing. If it was rich, HC and CO would be high, NOx would be low. If it was a leaky injector, HC would be high, but the others would be low. All 3 are high.

How old it the cat?

 

We bought the car 5 years ago. The exhaust looks stock and original.

Replacing the CATS is pricey. Is it possible to "de-tune" with LT1-Edit or tunercat to get below the limits?

 

It's a shame what they are trying to do to us. A year ago you could have bought a cat for $70-$200, but now every cat except dealer instlaled or magnaflow will cost $500-1,000 and hardly anyone will install another cat because it's illegal now. They have also recently lowered the max allowable #s for older v8's. You probably would have passed if they hadn't lowered the numbers.

If you can somehow get your hands on a cheaper cat, which would be hard because no one will ship it to CA, and find someone that will do it for cash. OR buy one of those cleaners you put in your gas tank called "Guaranteed to Pass Emissions". I thought it was crap until a smog tech told me to try it and it worked TWICE. I've got a cam and stuff that makes the numbers higher anyhow, but I still passed. Make sure you follow the instructions and run it through the full tank until it's nearly empty, then refill and go to smog station.