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Old 11-06-2002, 11:45 AM
Richard Wooldridge Richard Wooldridge is offline
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Join Date: Dec 2000
Location: Battle Ground, WA
Posts: 576
Excessive nox emissions...

Hi there,
I think you need to go back to the original problem, the high hydrocarbons. The reason I say this is that you have very high nox emissions. These are caused by excessively high catalytic converter temperatures. I'm thinking the reason your cat is so hot is because it's getting too many hydrocarbons, and burning off the hydrocarbons is overheating the cat converter. The EPA has released a report that states that catalytic converters are contributing to global warming by causing excessive nox emissions to occur, and this may someday be the reason for their eliminating catalytic converters on tightly controlled fuel injected gasoline engines. That's not going to happen overnight, however, so why don't you get the engine tuned up and fix the original problem? My 1982 Mercedes 300D with the 4.3 liter chev V6 installed passes with NO catalytic converter, with much lower hydrocarbon numbers than you are showing. It shouldn't be very difficult to maintain an idle speed hydrocarbon measurement of under 150 ppm, and a 2500 rpm measurement of under 75 or so. Those are the numbers my engine posted last emissions check. (Washington State) You can't fix an out of tune engine with a new cat!

Richard Wooldridge
1982 Mercedes 300D/4.3V6
1994 Ford Taurus
1988 Chev Astrovan
1977 Jag XJ6L
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