Ten years of testing vehicles and explaining so customers can understand was enlightening.
Sometimes it seemed easier to just get all the customers in the waiting room and
just have a class.
So lets have a short class for the basics.
Just as the human body is an amazing creation the automotive is similar. Pumps for fuel, pumps to cool, pumps to breathe and pumps to do alot of other things.
It is the orchestration of all these systems working together that make for potential perfection.
Now the science part. When your car is tested they measure 5 gases.
HC which is hydrocarbons, a pretty popular word these days.
Co which is carbon-monoxide a fuel.
Nox which is a sedimentary pollutant.
Co2 which is carbon dioxide
O2 which is oxygen
A tune up is not really a repair for emission controls, although it is the standard of operations to start to keep emissions in order. If you know you just had a tune up, and your car fails a smog test, you might have a inept mechanic or faulty or missing equipment in their shop. During a tune-up, the shop should check your gas readings to be sure they did nothing wrong, installed proper parts, and did not miss anything that needed repairing. That requires a technician with proper knowledge and equipment, otherwise you are getting maintenance. Maintenance is very important as well, but not a cure for failed smog test unless you have neglected your cars maintenance, which does happen.
You see the fuel has to be delivered in proper amount, too little or too much and you will have excessive HC's and maybe excessive Co, and usually lower CO2 and O2, possibly higher nox also.
O2 has to be delivered in proper amounts or you might get the same readings, along with high O2. so plugged or restricted air filters and broken vacuum lines or intake air boots being cracked, cause the air to be held back or sucked into the motor in the wrong place. This can cause major engine damage as well from what is called a 'lean' condition, burning spark plugs, valves and all sorts of bad results.
The low CO2 is a result of many things but often a weak catalytic converter, which can be tested very easily by a educated technician. So next time you are talking with your repair shop ask them how and see if they can tell you, then you will know what kind of shop you are dealing with. Write me back if you want to know and I will tell you also.
There is a term not used much anymore called diagnostic tune-up. It is just as it sounds, a few steps to check and see if things are in operating conditions to be efficient for emissions, usually the tune-up conditions are easily tested and a technician can dig into other systems to find a cause of high emissions. If a repair facility practices this it is not difficult, but it could be a foreign language to some.
Remember those lights on your dash aren't really for dummies, especially if the cel or ses or service engine or a picture of an engine start flashing, pull over asap to a qualified repair facility, or later you might feel like a dummy when you find out you have major engine damage.