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Emission Test failed question.


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All right it’s not my truck but this is the only forum I’m signed up with right now, so I hope you don’t mind. It is a 94 Pontiac T/A with about 64K on the odometer. It has the 5.7 engine. It is garaged and only comes out once a year or so. In this case since the last emission test. It is all stock and never had a problem in the past. The part that failed was the NO levels. All other levels were well below average. At 15 MPH the max level was 689, the average was 150 and I got a 748. At 25 MPH the max level is 706, the average is 136 and I got a 644.

 

My question is there any thing I can check with a minimum of tools (and skills) before going to an emissions diagnostic center? Also it stays garaged most of the time. I took it out and only drove it for about 20 miles in town before getting it in smogged. Would going on the highway for a hour or so clear this up?

 

Thanks in advance.

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Sounds like your EGR should be checked. EGR lowers combustion temperatures, reducing the formation of NOx.

 

If your EGR valve is not opening, due to it being rusted in place, or due to the vacuum dashpot leaking vacuum, it would lead to the emissions situation you've described.

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