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Car did not pass emission inspection

I have a 1994 Honda Civic EX-4 door with 300,000 miles. This is my third question for today.

My car did not pass its last vehicle emissions inspection. I very seldom drive this car now, but I want to keep it around as a backup vehicle. Do I need to drive it more in order to maintain certain emission levels?

My emission results are the following for idle/treadmeal exhaust emissions reading:

October 2007 Emissions

GPM = Gram per Mile

Hydrocarbons (HC) Standard: 0.9000 GPM

Hydrocarbons Failed Results: 1.7058 GPM

Carbon Monoxide (CO) Standard: 20.0000 GPM

Carbon Monoxide Failed Results: 34.3474 GPM

Oxides of Nitrogen(NOx)Standard: 2.1000 GPM

Oxides of Nitrogen Pass Results 1.5831 GPM

Actual CO2 is 249.2363 GPM for 4 cylinder engine

How can I find the emissions problem? What should I look for given these results above? What is the best correction?


You need a new catalytic converter and the EGR syatem is not working. You can’t count on that thing as a backup anymore. It costs too much to register and insure. Not to mention fix.

The have a thing called a car rental. They are the best bet for back up cars. In the long run they cost a lot less than owning a car for occasional use.


A car rental for one day can be as little as $30. I imagine that your Honda costs you over $100 to insure each year. You could rent for 3 or 4 days at least before you exceed the insurance savings. Your current auto insurance will cover you while you rent.

The emissions test results show that the engine is running rich, and isn’t burning that fuel well, and that NOx is high. A good tune up, with fresh spark plugs and wires, distributor cap and rotor, air filter, and pvc valve can help it burn fuel better.
For the NOx, it may need a catalytic converter. Retarding the timing, by turning the distributor 1/8 inch in the retard direction, can help lower NOx.
Then, you’ll have to erase the check engine light…probably, by disconnecting the battery for a minuet.

As I read the results of your test,
1.) Oxides of nitrogen are within spec. Not a problem.
2.) Hydrocarbons are high. That means the engine is running rich.
3.) Carbon monoxide is high. That also means the engine is running rich.

It’s pretty difficult to pinpoint this from a distance, but your most likely cause for this is a failed oxygen sensor (which gets my vote), a failed throttle position sensor, or possibly even a failed engine coolant temperature sensor.

Also consider as your car gets older, it is not going to stop having problems so you will still have maintenance and repair cost for that car, even if you don’t drive it at all. Not driving it often actually can cause problems.

JayWB is correct. The NOx are ok. you don’t need to turn the distributor to retard the timing to lower the NOx. The timing retarding CAN lower NOx, sometimes. I did it a couple of years ago on a car similar to your Civic (a 1989 Something [senior moment ]).
Still, do the tune up, spray the inside of the throttle body, and use MAF spray cleaner on the MAF (Mass Air Flow) sensor. Then, take it back through the emissions testing.
If if fails the re-test, check those things that JayWB, and the others, have advised of. You can have someone do the test of those sensors with an electrical multimeter. The instructions, and ohm/voltage values, are in the repair manual (Haynes, or Chilton’s) that you SHOULD have.

Howdy, when last tune up? How long did ya drive it before having the test. Consider adding a can of sea foam to 1/4 tannk of gas and change oil and drive the gas out then retest. Just might pass .

Also make sure to run the car for at least a half hour on the highway before you test it again.

Shadetree, I believe the HCs and COs are too far above minimum to correct this easily. There is a serious problem with fuel control to run this rich. Jus’ sayin’.

I think the O2 sensor and MAP sensor needs to be evaluated. Sad part is, these ODB-I systems are dumber that the ODB-II, and this will require using testing procedures if no codes are present. My 1988 Supra had a similar, but not a bad, problem. After some testing, the O2 sensor was found to be bad, and not sending any voltage, but no code was present. I suppose the computer checked, and yes, there was an O2 sensor. I did get a code when I unplugged it, tho. Just to see if the computer was working.