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NOX problem update 200

Did a little more troubleshooting into my high NOX problem today. Checked both ignition and fuel injection codes for failures. Did have the 2-3-1 fuel system compensating for rich or lean air/fuel mixture with no check engine light igniton had no fail codes. Did the propane test with no change in engine speed. Pulled out back spark plug and noticed some wetness. My guess is unburnt fuel didn't seem like oil. Pulled #2 plug noticed no wetness and maybe a slighly too hot condition.

My theory.

Dirty back injector causing bad spray/rich condition in back cylinder. Oxygen sensor senses rich conditions and compensates by leaning out mixtues cause hot combustion and high NOX reading.

Any opinions?








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    NOX problem update 200

    Many times the cylinder that shows it to be running rich is not the one that is causing the trouble. It is usually the cylinder(s) that shows the lean condition that has the problem. Lets say the injector in the 2nd cylinder is partially plugged. The oxygen sensor will notice the lack of fuel and will try to correct the problem and supply more fuel. This may get the fuel mixture in the 2nd cylnder closer to the correct air fuel mixture, but in the process will make the other cylinders run rich with fuel and would show up as dark or black sparkplug porcelains. Can you have a cylinder balance run on the engine to check out the power differences between the cylinders? This would point to the troublesome cylinder/injector.
    Happy New Year!!!!
    John








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    NOX problem update 200

    Sounds logical, since high NOX is basically incomplete fuel combustion. By the way, my local Volvo guru told me that many older Volvos are failing E-Checks with high NOX being the most common.....my car was still out of spec (failed) after adjusting fuel-air mixture, retard timing, looking for vacuum leaks, etc. Since I spent money to have it looked at, the state gave me a waiver in order to get plates. The car runs perfect and gas mileage is fine. NOX testing is new this year for most states.

    Jay
    84 245 GLTi 226k








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      Whoa there now!!! 200

      NOx is NOT caused by poor combustion. NOx is created when there is an excessive amount of air present during combustion. The oxygen in the air combines with the fuel over a very short time period, releasing all the heat in the fuel at once. The high temperature allows the nitrogen (nearly 80% of air) to combine with any left over oxygen, creating NOx. If there is less air present combustion will occur over a longer time period, releasing the heat more gradually, creating less NOx. If there is less air present there will be fewer O2 molecules left over to combine with the nitrogen.

      Incomplete fuel combustion will produce high levels of carbon monoxide and hydrocarbon at the tail pipe, usually caused by a lack of sufficient air to support combustion, or by poor fuel atomization (bad injectors) that interferes with the combustion process.








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      NOX problem update 200

      Heard the same thing about alot of Volvo's failing for NOX. Probably related to the fact we drive them for so damm long!!! My 1990 has no idle mixture control and timing is set electronically. In RI to get waiver need to spend $450.







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