FREE ASE PREP: Hydrocarbons
Another page from my ASE/ BAR SPECIFIC Diagnostic Course Smog License.
What are automotive Hydrocarbons or HC?
You properly heard this phrase if your car fail smog and it has high HC’S, change the Catalytic Converter and your car will pass an emissions test, but here is the problem.
Your car is driving poorly, it’s wasting gas or your vehicle has a misfire, if you change the catalytic converter you may pass an emissions test the first time, but you will be wasting money.
When the Catalytic Converter is replace without fixing the problem then the CAT is acting like a band aid. Replacing the CAT will not improve your gas mileage or performance if you vehicle is running poorly.
If a vehicle has high emissions you need to find out why before you change a Catalytic Converter.
Here is the important part; a MIS FIRE will Kill a New Catalytic Converter!!
So let me explain this automotive emission to you.
HC is measured in parts per million or ppm, a good running computerize vehicle should read 50 ppm or less out of the tailpipe.
If the vehicle has a misfire, runs lean or has lack of compression, or even runs rich, HC will be high.
Here is a list of common problems for high HC’s:
Vacuum Leak or Lean Condition:
If there is too much air it will act like an isolator and prevent some of the fuel from burning and HC will leave out of the tailpipe.
If the engine is running to rich there is not enough air to burn all the fuel, there will be left over HC. Hydrocarbons will then leave the combustion chamber, and then come out of the exhaust.
Ignition system problems:
Bad plugs or spark plug wires, over advance timing are common failures for HC. If a spark plug doesn’t work or a plug wire doesn’t ignite, this means the gas doesn’t burn.
It leaves the combustion chamber and tail pipe as unburned gases. A bad wire can cause HC to be over 1500ppm
Mechanical Problems with your Engine:
Lack of compression or mechanical problem with the engine will also cause high HC because the cylinder walls will not being sealed properly and causing poor combustion.
An example would be a burnt valve from the intake or exhaust will interrupt the compression process and the un burnt gases will leave the combustion chamber then out the exhaust.
A blown head gasket will prevent compression from building up and vaporizing the fuel correctly also.
Emission control component not working:
Air injection systems not operating correctly can cause high HC and High CO. An EGR valve not working correctly either not closing or opening to soon will cause an increase in HC and a performance problems.
Now I know most people have heard change the Catalytic Converter, that will lower your emissions. Well this is true but confirm that everything pre and post combustion are working correctly.
FREE ASE PREP: Hydrocarbons
The reason is putting a Catalytic Converter on a car with an ignition problem will kill the Catalytic Converter fast.
A Catalytic Converter should be the last thing you change fix the cause the high emissions first then concentrate on the Cat.
When a Catalytic Converter is efficient the HC, CO and Nox will be burned and you will have lower emissions.