Hello,

I have a 91z28 camaro, with a 305 tpi and auto trans that just failed emissions testing in Chciago IL. I failed the maximum level for hydrocarbons(HC) standard is .80 my car produced .89 while on the chassis dynometer cruising at 55MPH. The carbon monoxide (CO) reading was 15.0 GPM, standard was 15.0 GPM. The carbon dioxide (CO2) reading was 446.4 GPM. Car was tested warm (200 degrees) with mid grade fuel, no codes recently.

This car flew through this test 2 years ago, with HC readings of .574, CO of 6.529 and CO2 readings of 3.401. As you can see my overall emissions had gone up in every category.

I have not really changed anything to this car since the last test. It is pretty much stock, with 28000 miles, original cat, new injectors 3 years ago, oxygen sensor was replaced approx. 5 years ago and has about 10,000 miles on it.

I am thinking of starting with plugs, wires and maybe a new oxygen sensor.

Any ideas on what else I should do to get this to pass?

Thanks!

 

I would do..
-plugs
-wires
-cap and rotor
-fuel filter
-air filter
-oil change
-o2 sensor

Also check the Purge Canister.. those don't last forever either.

Do you have Diacom or such? that will help to tune the car a bit as well

 

You are so close to passing that I would just do the following:
1. Put in 87 octane fuel.
2. Check the base ignition timing. Factory spec is 6 degs adv. I would retard it slightly to 4 degs adv.
3. Get the motor hot before you get there. This helps the combustion efficiency.
Email me if you need help.

www.geocities.com/dzperf



------------------
D&Z Performance
"Putting Power to the Pavement"

 

Thanks for the help guys, I did have the motor hot before I went in and since I feel a slight miss at idle I will check the plugs, wires, cap and rotor before my next attempt. If this smooths out the idle I may go for it then.

I don't have a diagnostic tool at this time.

How do I check the purge canister?

I will keep you posted!

Thanks again!