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High HC means its running rich, high CO usually means your Catalytic converter is clogged or inefficient. There are many reasons for this but in my experience the main one is a faulty O2 sensor giving the wrong signal to the ECU. You should have noticed that your fuel consumption had increased (or your miles per gallon had decreased) at about the same time yourO2 sensor failed. It is worth getting a diagnostic check done on your vehicle to try and confirm this. Suspect new cat needed but you still need to find the cause otherwise you will ruin your new cat
Failing HC and CO means the fuel mixture is too rich.
You may need a 4 gas analyzer to figure out why to know when it is fixed. Could be a leaking injector, restricted air intake, ignition problem, or a long list of other things. Even a faulty thermostat could cause it to run rich.
i can be, only 2 things, or both. 1: engine running way too rich. 2: dead cat. (both happens, too) replace the cat, might be cheaper that full engine diagnosis and repair. in a real shop we test the cat. using up and down stream tests. with the 5 gas analyser. but the truth is a new CAT can hide a very filthy running motor.
Here is some info for you to read, besides me explaining what ppm is, i also gave you some info of how to solve this, Ain't that special LOL. Mike
Overall Result: PASS or FAIL. A vehicle with a properly operating engine and catalytic
converter will have very low HC and CO readings. However as a vehicle ages the HC and CO
emissions will increase and may become erratic. As a vehicle ages it becomes increasingly
important to be sure that the engine and converter are fully warmed up before the test to
have the best chance of passing the test.
HC (PPM): The parts per million of hydrocarbons (unburned or partially burnt gasoline)
in the exhaust.
CO (%): The percentage of the exhaust that is carbon monoxide (CO).
CO +CO2 (%): Complete combustion in the engine or catalytic converter will result in very
little carbon monoxide (CO) and a high percentage (up to about 16%) of carbon dioxide (CO2)
in the exhaust.
O2 (%): When there is complete combustion in the engine or catalytic converter there is a very
little oxygen (O2) in the exhaust. Usually less than one percent. A higher reading indicates a
problem with the engine, the exhaust system, the sampling system or the catalytic converter.
Vehicles do not pass or fail because of the O2 reading; it is only diagnostic information.
RPM: The engine speed in revolutions per minute (RPM) or N/A.
Cruise Limit: The maximum allowable HC and CO emissions at 2500 rpm. The CO+CO2 (%)
must equal or exceed 6. This verifies an adequate sample of the exhaust has been obtained.
N/A for O2 and RPM.
Cruise Emissions: The emission readings measured at 2500 rpm.
Cruise Result: PASS, FAIL or N/A.
Idle Limit: The maximum allowable HC or CO emissions at idle. The CO+ CO2 (%) must equal or
exceed 6. This verifies an adequate sample of the exhaust has been obtained. N/A for O2 and RPM.
These are the possible problems:
bad o2 sensor
bad EGR valve bad cat bad timing
bad plugs or wires
the less costly fixes include replacement of the o2 sensor and EGR
valve i would not clean the EGR I would buy a new one there are very
cheap you can pick these up at any local parts store .
also run some injector cleaner through your car at least a full tank of
gas and one bottle of injector cleaner should be ran through.
you can also have your timing checked for a relatively low price.
and when you go into to have the vehicle checked make sure the car is
been running because your cat convertor has to be warm in order to
preform at it peak so do not do it when the car is cold.
all of the above are pretty reasonable fixes the general rule of thumb
when you work on your own vehicle is start with the cheapest fix first
then go on to the next.