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mazda94lx

Failed Low Idle Emissions--Hydocarbons

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Hi Folks,

Just got back from inspection, passed high idle but failed low idle emissions for hydrocarbons only (400) threshold is 220

Passed CO easily and NO. Idles fine, no smoke or oil burning/leaking. No codes.

With above said, what causes this and what are the probable fixes?

Tks!

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I think you have two choices. The obvious one is that you need a new catalytic converter.

The other choice is to drive your car on a fairly long high way trip to clean up the catalyst as much as possible and try again- no guarantee to work.

Considering by how much you are failing, I' d say go for the new catalyst.

Last time I could not pass because of a 102 reading on hydrocarbon (100 is the max allowed here). :(

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I think you have two choices. The obvious one is that you need a new catalytic converter.

The other choice is to drive your car on a fairly long high way trip to clean up the catalyst as much as possible and try again- no guarantee to work.

Considering by how much you are failing, I' d say go for the new catalyst.

Last time I could not pass because of a 102 reading on hydrocarbon (100 is the max allowed here). :(

The converter is fairly new, changed within the last 7k. Funny thing though, is the one before that basically disintegrated from the inside causing the car to choke and stall-- that one was also fairly new when it crapped out.

The car was idling a very long time in state inspection line here--NJ.

Any other suggestions?

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A fuel/air ratio slightly rich will usually cause a low hc,but high co reading.

Whereas a slightly lean fuel/air ratio usually causes a high hc,but low co reading.

A possibility of high idle hc reading could be a small air leak on the inlet manifold,this would have more effect on idle than fast idle ?

I would suspect the inneficient cat to cause higher co and hc levels.

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I think you have two choices. The obvious one is that you need a new catalytic converter.

The other choice is to drive your car on a fairly long high way trip to clean up the catalyst as much as possible and try again- no guarantee to work.

Considering by how much you are failing, I' d say go for the new catalyst.

Last time I could not pass because of a 102 reading on hydrocarbon (100 is the max allowed here). :(

First off, Anytime the HC's are high and the other numbers look good, you shouldn't go trying to replace the cat. The cat mostly takes care of

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