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A leaking exhaust pipe can cause this sort of issue. If there is a leak before the oxygen sensors, air can get into the exhaust causing the sensors to give an erroneous lean reading back to the ECU. To compensate, the ECU will add more fuel causing a rich mixture and hence a test failure. The leak could be in the exhaust down pipe or even within the ...


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HC-PPM means hydrocarbons in parts per million, when this is high it means there is lots of unburned fuel in your exhaust, this is either due to your engine running too rich, or a misfire in one cylinder. Usually running rich leads to an increase in CO emissions, but your CO emissions look fine, most likely your problem is due to a misfire in one of your ...


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This is an EXCESS UNBURNED HYDROCARBONS (i.e. FUEL) condition. For some reason too much unburned fuel is coming out the tailpipe. Some common causes: Bad or worn spark plugs. Try changing with new ones that are properly gapped. Defective ignition coil(s) or wires. An engine analyzer should show which cylinders are failing. Defective catalytic converter. ...


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