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Emissions Test Failure


ixousdan's Avatar
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10-23-04, 11:01 AM   #1  
Emissions Test Failure

1995 Geo Prizm - maintained well, no smoke, no loss of power, but suddenly this year it failed the emissions test required in my county, due to Low Speed HC and NOx.
Would an auto parts shop plug into my computer for free and give me a code?
Does the code usually lead you to the problem?

 
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10-23-04, 06:26 PM   #2  
cbmf
autozone will test
disconnect battery then reconnect andthe codes wills not show up on the test test until you start the car three times

 
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10-23-04, 08:19 PM   #3  
How high are your readings? You may just need a tune up and an oil change to bring these numbers down. Then again it may be a little more involved.
Post the numbers and the limits for you vehicle in your state and maybe we can help diagnose it more thoroughly.
Hope this helps ya,
Billy

 
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10-24-04, 04:12 PM   #4  
Emissions Test Results

These two items failed for the Low Speed Emission resutls(15 mph)
HC(ppm) - Standard 152 .... Current 501
NOx(ppm) - Standard 1186 ... Current 1636

The car has 134,000 miles. After the test I changed oil, spark plugs, Air filter, used gas additive/carb cleaner. I have not been back for a retest.

 
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10-24-04, 04:23 PM   #5  
Does your state also test Carbon Monoxide (CO)? If so what are the specs?
Billy

 
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10-24-04, 05:09 PM   #6  
Pollutant Hi Speed results (25mph) Low Speed Results(15 mph)
RPM 1875 RPM 1676
Standard Current Reading Standard Current Reading Reading
HC(PPM ) 147 147 pass 152 501 FAILED
CO(%) 0.82 0.22 pass 0.85 0.57 pass
CO2(%) 14.2 13.6
O2(%) 1.0 1.5
NOx(ppm) 1072 497 Pass 1186 1636 FAILED
DILUTION(%) >6 14.4 >6 14.2

Thanks for your analysis.

 
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10-24-04, 05:26 PM   #7  
You mentioned you would like to get your computer tested for codes. Is your check engine light on? If so, it may not be able to be read by a parts store because its not OBDII compliant. But it wont hurt to check. If the light is on get the codes read and post that back.

 
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10-24-04, 05:27 PM   #8  
Dadealus
First off, was the engine fully warmed up? The catalytic converter needs to be at 900*F or higher to be really effective.

 
ixousdan's Avatar
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10-24-04, 08:19 PM   #9  
My engine light is not on. I just assumed the computer would give me a code on a bad part since I failed the emissions test. I was looking for a code to give me a place to initiate a repair to improve the emissions. The engine was warmed up when I arrived at the inspection station, but there was about an hour wait before I got the results.

 
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10-25-04, 08:14 PM   #10  
NOx failures are usually a result of defective/non-functional EGR system, extremely lean air/fuel ratios, over-advanced ignition timing or high engine temperatures.

HC failures can be caused by lean air/fuel ratios, improper ignition timing, vacuum leaks, defective plugs, wires or other ignition components that cause a misfire.

If it were me, I'd check to make sure the EGR system is functioning properly and timing is correct and go from there.

All things being equal, the catalytic converter (unless poisoned by an overly rich fuel mixture, coolant, oil burning or a misfire) should still be in good shape. A catalytic converter efficiency test should tell.

Matt

 
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