Bought a used 1995 Honda Civic DX. Took it to get the tags and it failed the emissions test. HC (PPM) CO % Low High Low High Reading 245 443 3.27 10.02 Limit 220 220 1.20 1.20 Was told to get it tuned up. What would cause these problems? And can it be fixed/tuned up by a novice DIY mechanic?
This is most likely a tune up issue. The HC is unburned hydrocarbons. That is from running rich. The high CO is carbon monoxide and it is due in part to a rich condition but could be related to EGR valve. Yes you can do it yourself.
Emission test by codes reader? or smog? Any codes?
SOURCE: what will bring readings into limit
A failing oxygen (O2) -sensor will give failing emission tests. Normally you also get other symptoms:
- too high fuel consumtion
- bad acceleration, stalling problems, sputtering
- the check engine light comes on indicating that the engine control
unit has recorded error codes (which will be related to readings of
incorrect fuel/air ratio when read by the OBD diagnostics tool at a
repair shop).
It is always a good idea to see if you can get any readings from the
check engine light if present or much better by an OBD reader to be as
certain as possible.
Another component that could cause failing emissions tests is the
catalytic converter, giving a similar range of symptoms. To determine
if this is the cause is not so easy on older cars with only one O2
sensor, it requires diagnostic skills and equipment. On newer cars with
OBDII-systems it will give a recognizable fault code for the cat
converter.
Then there are also the issues of the actual cause of malfunction in
either or both of these components, is it due to old age and normal
wear and tear or is it due to contamination from burning oil (blue tail
pipe smoke) or anti-freeze (white smoke), misfiring, etc? Then the cause must be treated as well for a successful repair.
Normally
these components have a very long life span and
should not have to be replaced more than once or maybe twice for the
sensors during the car's lifetime in an otherwise health engine.
Good luck!
SOURCE: failed smog check
How well does the vehicle run?
Assuming that the engine did pass the EGR function test on the emission test results, and the MIL (Malfunction Indicator Light) or check engine light is not on when the engine is running, and if you are not sure when the last time it was that the engine had a complete tune-up, with distributor cap, ignition rotor, spark plugs, spark plug wires, air and fuel filters, then a complete tune-up would certainly help, and if the engine oil and oil filter have not been changed in a while, then they should also be changed before an emission test because long used engine oil traps carbon and it will show up as higher CO on the emission test because the emission analyzer will be able detect the higher CO from the engine oil through the PCV valve.
However, it would seem from those HC readings that there is a vacuum leak, and carefully inspect all of the vacuum lines for any cracks or damage, (especially the vacuum line to the fuel pressure regulator) because cracks in the vacuum lines seem to like to hide underneath the lines.
The emission label under the hood should have the vacuum line routing diagram printed on it, and the vacuum lines should all be checked to be certain that they are all connected correctly.
Here is the firing order diagram for that vehicle to help assist you tune-up the vehicle.
SOURCE: My 1997 Honda Civic failed
Jose, I don't know if this will give you the answer you are looking for because there are many things to consider here. The exhaust gas recirculation valve (EGR) is one of the main things involved in reducing NO emissions. This valve is controled by the power control module. (PCM) This is your vehicles computer. The PCM monitors the vehicles speed and will command the EGR to open when the vehicle attains a certain speed, which is why the ASM test being done is recorded at two different speeds. At 25 MPH your vehicle failed the hydrocarbon (HC) emissions limit and this could be for a number of reasons. When is the last time you car was tuned up? Old spark plugs, wires, clogged air filters, oxygen sensors, leaking injectors (personal experience) or the PCV valve could be contributing to the results of the test. I guess that the easiest way to go is to tune up the engine replacing the spark plugs, wires, air filter and the PCV valve and don't forget to have the oil changed at the same time. Only then should have the vehicle retested and see what the results are. Should it fail again you may have to consider having the EGR or the catalytic converter replaced depending on what portion of the test fails. If the NO fails I would consider the EGR. If the HC fails then I would consider the catalytic converter. Good luck with this.
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