California: 1991 Honda Accord SE, A/T
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| HC | CO | NOx |
| ||||
RPM | Max | Meas | Max | Meas | Max | Meas | CO2 | 02 | |
15mph: | 1854 | 118 | 13 | 0.75 | 0.08 | 799 | 1206 | 15.2% | 0 |
25mph: | 1912 | 93 | 11 | 0.63 | 0.05 | 738 | 1211 | 15.2% | 0 |
New O2 sensor, ran Seafoam, cleaned egr and ports, Egr function properly, Aftermarket CAT 2yrs old, CAT passed backpressure test and no rattling or smell, cleaned IAVC screen.
NOx levels dropped to low 900’s on pretest after cleaning egr ports. Still a hundred to high
Any ideas? Additives? Tricks to pass?
At trick is to drill several holes after the catalytic converter this mixes in more air and dilutes the NOx.
A new converter would help. Back pressure test just lets you know it isn’t clogged, doesn’t mean its doing its job….
Replace PCV valve
Run 94 Octane with Octane Boost(try to reduce early detonations and heat)
How To Improve Your Odds Of Passing An Emissions Test
The best way to improve the odds of passing an emissions test is to maintain your vehicle. A well-maintained engine is usually a clean engine as far as emissions are concerned.
Changing the spark plugs, air filter, fuel filter, PCV valve and oil regularly (or just before an emissions test), checking ignition timing and adjusting the carburetor (if you have an older vehicle) can reduce emissions and greatly improve your chance of passing.
Also, filling up your fuel tank with gasoline that contains 10% ethanol alcohol (many premium grade fuels use alcohol as an octane booster) may help lower your emissions even more. Many areas now have “reformulated” gasoline that contains alcohol or MBTE that adds oxygen to the fuel to reduce carbon monoxide and hydrocarbon emissions.
Just before the test, make sure your vehicle is at normal operating temperature. Take it out for a short spin down the expressway. This will heat up the oxygen sensor and catalytic converter to minimize emissions
high NOX usually indicates excessive combustion temperatures……is the car running hot? does it ping? is the timing too advanced? or is the EGR simply not working correctly…..considering this is under load at cruise……when the EGR should be doing it thing…..as in diluting the combustion mixture with spent exhaust….I would say its probably “clogged”…..you may have to actually take the EGR off and get the passages cleaned out with some carb cleaner and a small bottle brush? I have seen these thing completely plugged in the past…….
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