The Z didn't pass smog yesterday due to a high HC and CO

I attached the results and was wondering what caused this to fail.

Car is Stock

Replaced Spark Plugs

New Fuel Filter, Air Filter

No vacuum leaks.

Could this be a bad CAT? or Timing is set incorrectly?

Thanks for the help

Pat

I have a 1977 280z

Unburned fuel. Leaky injectors or EGR.

In the future get a pre-test done, or whatever they call it before its an official test that is reported to the state. That "GROSS POLLUTER" phrase is NOT a good thing to have associated with your car.

It's times like these that I'm glad I don't live in CA.

Timing is supposed to be checked by the smog tech during the test. (2 degree variance from spec. allowed last time I checked)

Does your car have a catalytic converter?

You do not list the mileage or how it is running.

Modifications?

Did you change the oil?

If it's badly fuel diluted it can cause higher HC/CO.

Now that you are listed as a gross polluter I believe your car must now be re-checked at a state referee station and if it passes, checked annually.

I'm betting a dead cat maybe caused by a misfire, leaky injectors, low compression (tired engine), or just old and used up.

Keep us informed on your journey.

Unburned fuel. Leaky injectors or EGR.

I checked the injectors today and no leaks, all vacuum hoses are good, EGR no leaks

In the future get a pre-test done, or whatever they call it before its an official test that is reported to the state. That "GROSS POLLUTER" phrase is NOT a good thing to have associated with your car.

It's times like these that I'm glad I don't live in CA.

I didn't know that if it fails, it will say on the paper about being Gross Polluter, since this is the first time I failed on a smog test.

CA is such a PITA about smog.

Timing is supposed to be checked by the smog tech during the test. (2 degree variance from spec. allowed last time I checked)

Does your car have a catalytic converter?

You do not list the mileage or how it is running.

Modifications?

Did you change the oil?

If it's badly fuel diluted it can cause higher HC/CO.

Now that you are listed as a gross polluter I believe your car must now be re-checked at a state referee station and if it passes, checked annually.

I'm betting a dead cat maybe caused by a misfire, leaky injectors, low compression (tired engine), or just old and used up.

Keep us informed on your journey.

Where are the ignition timing mark located? I can't find those degree numbers on these cars

It has Catalytic Converter. I will try to replace them tomorrow. Looks like it is still original. Muffler shop charges $180 installed.

I don't know how much miles is actually on the car, Engine is original reading 15k, might be 115k, 215k, 315k, no clue.

Oil is around 3000k on Castrol synthetic 20w50

Change the Cat and I bet you pass. Everytime one of my cars fail, I change the cat and then the car passes.

I didn't know that if it fails, it will say on the paper about being Gross Polluter, since this is the first time I failed on a smog test.

You have to fail by a certain amount to be consdered a gross polluter. You reached the gross polluter status based on your CO reading. Your HC, though failing, was below GP status. I concur with Montezuma. Those readings, in my experience would also lean towards a bad cat.

You really need to take your car to someone that has more technical expertise before throwing money without knowing what's wrong.

A factory service manual along with some diagnostic equipment really are good to have if you plan on keeping this car.

A misfire or low compression on a cylinder or three can cause elevated HC & CO. And that's just one of many possible causes.

Cat may be bad and I guess you will find out after spending $180.

BTW: Cali has some new cat converter replacement rules.

I'm sure the referees will tell you if the cat installed was correct or not.

Your journey continues.

Edited March 17, 201114 yr by H4LIGHTS

Here is some research material for you: Tony D's smog wisdom

If you are living in California, Tony D's experiences and research will help you. Focus on the more recent posts to look for changes in the laws.

Really good infos.. Thank you so much for the advice. I will let you guys know the results next week.

Good Day.