unburned fuel at tailpipe

1990 BUICK LESABRE
200,156 MILES • 6 CYL • FWD • AUTOMATIC
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CUSTOMLE90
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  • 1 POST
My vehicle runs fine but it will not pass emissions test. How can I reduce the amount of unburned fuel at the tailpipe? Fuel pressure gauge, EGR, MAF, Ignition wires, water temp sensor all checked or replaced. Split fire plugs may be employed.
Dec 23, 2008 at 8:56 PM
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KASEKENNY
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If you are failing due to high hydrocarbons, then the most likely cause of this is the converter has failed and is no longer reducing the emissions enough.

Here are a couple guides that will help with this:

https://www.2carpros.com/articles/smog-test-inspection-information

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

If you have no engine issues other, than it is failing this test then I would suggest changing the converter and then having the vehicle retested.

Please see the info below on this and let us know what questions you have.

Thanks
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Nov 12, 2021 at 10:53 AM