Failed smog

You failed with high NO. Causes are:

1. your engine is running too hot
2. Too lean, too much air not enough fuel, (a vac leak?)
3. Bad cat, although this would also see a higher HC number

 

Yes, the HC is a little high but not quite failing. is it stock CATs or hyperflows?
I would chase down the engine running hot too. It is cheaper.

 

My guess is, the cats are shot.

 

Bingo! Notice the second test was a pass at the higher MPH test with sufficiently low NO. Low speed test was a fail on NO. Seems associated with the idle problem mentioned. O2 looks a little high too.

 

High NO is usually caused by a lean condition. I recently went through a very similiar situation with a C4 Corvette and had very similar readings to yours. In that case it was a bad EGR valve but bad O2 sensors or a vacuum leak can produce similar NO results.

 

Unless Euro cars don't have post cat O2 sensors, he would be getting catalyst efficiency below threshold codes.

 

My 99 had similar rsults when post O2 sensors were getting older. I found the stock cats could make due with poorer O2 sensors but my hyperflows were very sensit ive to the O2 sensors.

When I put in new O2 sensors my hc numbrs drop to below 8 and then the no numbers passed easily with tubi headers , hyoerflow cats and capristo twin valve.

Summary from me replace both O2 post cat.

 

Why guess? Measure emissions for both banks at the sampling ports. That's why they're there.

 

Good point.

 

The more likely offender is the pre cat O2 sensors ....not the post cat O2 sensors. The job of the post cat O2 sensors is to determine if the catalytic convertor is working properly. If you look at the signal off a pre-cat sensor it usually has a lot of fluctuation. Over time, that signal can deteriorate to a point that it creates a lean condition that the sensor and the ECU thinks is normal. A normal operating post cat O2 sensor has very little fluctuation which means that the catalyst is working properly. If not, you get the "catalyst efficiency below threshold" code.

You do need emissions equipment to test it. Short of that, putting in a couple of pre-cat O2 sensors may solve it.

 

Will these cars pass smog with test pipes and 02 extenders, assuming there is no CEL ?

 

Nope. The smog will be measuring the HC that the lack of cats are not removing

The O2 Extenders are just a way to fool the ECU

 

Like others said

Weak 02 sensors
Vacuum leak upstream
May have fried the cats along the way

Mark will find it

Found tons upstream leaks in mine and was running good


[ame]http://www.youtube.com/watch?v=94Q-rs9bDO4[/ame]

 

Depends o your state. If they just check codes yes. If the also do a visual inspection for cats, not. If the require a sniff test, not.

 

Assuming no visual or sniff test and I've fooled the ecu for CEL. We just do the OBDII plug in here.

Good to go ?

 

Hi Skipp, if your state only connects to OBDII, no cel and you pass (assuming readness monitors are proper)

 

Thanks guys. Installing these items soon and appreciate the insight.

 

Personally, after looking at the cats, I think that it is running lean, suggesting to me that it is either a leak (which I doubt, but remains plausible) or deterioration of the O2 sensors.

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