Failed NJ Emisisons - Help?

[nj300se]

Well, for those who might still be concerned, I PASSED!
I changed my air filter, plugs, pcv. Cleaned my EGR tube thingy (which was not clogged), cleaned the TB as best I could, ran a tank of Tecron for a week, and lastly I changed the oil. Before the test, I filled it with Shell 93 and I had it on the highway for a good 40 minutes before the test and kept the RPMs up most of the time trying to blow out any ________ and get the cat hot.

Here's the before and after numbers...

First failed NOX reading was 1788, I passed today @ 726!
First HC failed @ 187, today I passed @ 58!
CO was OK then @ .43, today it read .17
CO2 was OK then @ 12.4, today it was 15.5
O2 was OK then @ 1.5, today it was .5

Not sure what to make of the numbers except that it passed and I am good for another 2- years with this car! Not sure what threw the numbers out-of-whack in the first place, or what "fixed" it. I was just happy I didn't have to get a new CAT or EGR valve.

Thanks for all the advice and info!

 

[Quickbeam]

Glad you passed. I missed this thread but as an emissions tech (and in all modesty a good one

) I wanted to compliment vizvo on his excellent and technically correct post.

 

[oldmaninsc]

Quote:

---

Glad you passed. I missed this thread but as an emissions tech (and in all modesty a good one

) I wanted to compliment vizvo on his excellent and technically correct post.

---

Serious question for you - I noticed the poster said he ran "Shell 93" for a week before testing - obviously high (or higher) octane fuel. I have heard a number of people say they do the same thing before an emissions test. In your opinion, does this help or hinder? I know a little about cars and already have an opinion, but I'd really like your 2 cents. Thanks!

 

[Quickbeam]

Since I'm more of a practical tech than a theoretical one I should know better than open that can of worms but I'll tell you what I've been taught. It's not a simple answer. If you use less an octane than the engine was designed for it hurts. If you use more it helps a bit but only a bit and only to a point. After that it can hurt. It also depends on what the fuel was octane boosted with. Ethanol will reduce emissions somewhat more than most other chemicals for example.

I was taught, and it's supported by theory and testing that generally, all else equal in a healthy engine, as octane increases CO and HC decrease but NOx increases. However go beyond a certain point in octane and HC and CO will drastically increase but even when this happens the catalyst's efficieny may be good enough to clean it up. (Remember, it's what comes out the tailpipe matters even if your engine is being trashed). So if you're asking if one should use the highest octane available during a test then no, studies show that's a bad thing. Better to use a midgrade. Even then it's not likely to help. It might squeak you by or it might not depending on which of the gases are high.

On the other hand usng too low of an octane can contribute to deposits which will increase emissons over the long term. When testing time comes you'll need to get rid of these deposits to lower HC levels but again, the cat may take care of that if it's healthy enough. Also, using a higher octane on an older vehicle often will reduce emisisons. Me, I use a midgrade at all times but I do it to balance costs vrs deposit control. I don't sweat emissions because I have the equipment to keep the emissions on target or repair it when it goes off.

Reading the poster's numbers he wasn't in that bad shape to begin with. I believe his passing was due partly to the maintenance he performed and partly to not having the catalyst at temperature during the first test. If everything else is working (O2, good igniton, etc) it's always best to go into a test with low time oil. I often plan oil changes and other maintenance based on my emissions test month. Makes it easy to remember.

If that's no help you can always spring for SAE Technical Paper 2002-01-1664

http://tinyurl.com/ybkhs3

As I said there's no simple answer. If you want one I'll say use the recommended octane for the engine (or one grade higher) and increasing it for the test will do nothing in nearly all cases. Not only because of the limited effect but also because engines that fail always have a problem elsewhere, a problem octane or any "magic in a bottle" can't solve. There are no magic cures for emissions problems in spite of all the hype out there. The bottom line is if the catalyst is healthy and being fed a stochiometric mixture the vehicle will pass. It's how it the engine was certified in the first place.

 

[nj300se]

The reason I used the high octane for the test was because "vizvo" posted "Avoiding detonation will prevent NOX. Always run high octane gas when you want help passing a NOX emissions tests." Normally, I put 87 in the car, and that is what I had for the first test.

Filling up with 93 was an easy thing to do for me, so I did it. Don't know how much it contributed, but it obviously didn't hurt!

I'm pretty sure that coming right off the highway to a scheduled appt (no wait) was a big help, compared to idoling for an hour on line before the first test.

Its all pretty much beyond my understanding, but I find it interesting nonetheless! This is a great board!

 

[oldmaninsc]

Quote:

---

I was taught, and it's supported by theory and testing that generally, all else equal in a healthy engine, as octane increases CO and HC decrease but NOx increases. However go beyond a certain point in octane and HC and CO will drastically increase but even when this happens the catalyst's efficieny may be good enough to clean it up. (Remember, it's what comes out the tailpipe matters even if your engine is being trashed). So if you're asking if one should use the highest octane available during a test then no, studies show that's a bad thing. Better to use a midgrade. Even then it's not likely to help. It might squeak you by or it might not depending on which of the gases are high.

---

First, thank you for taking the time to reply. I have to say I agree (FWIW) with what you said. My personal experience has been the same. I am not a professional, but I have helped MANY relatives and friends get their vehicles to pass smog over the last 20+ years.

Back in the days when they only measured HC and CO at idle and 2500 RPM (or whatever the number was) I think premium fuel was a good thing to use - at least for testing purposes. I don't know about other states, but here in Ca. they have been doing the dyno type test for several years.

I have a 95 Ford Aerostar with the 4.0 engine. I bought it when it was about a year old with about 20K on it. Needless to say I've had to get it "smogged" several times. The one time that I used premium in it before a test, I found exactly what you said - the HC and CO were slightly lower, but the NOx was considerably higher though still within max allowable range. This vehicle does NOT have an EGR valve. It was designed to run on 87 octane. It's been a very reliable vehicle. Currently has 190K on the odometer.

California puts this vehicle in the "gross polluter" category, so I have to get it tested at a "Test only" station. In Feb. 2005 I had to get it smogged for registration purposes. I had been sick for several weeks, and decided - what the heck I'd just go for it. Usually I change/check the plugs, wires if needed, change the oil, change the air filter, etc. before going to the test. Since I was sick, I just got in the vehicle, drove 3 miles on city streets, pulled up to the shop and told the guy "I need a smog test" He pulled it right in, tested it, and when the computer was printing out the paperwork he was shaking his head. I thought - Oh no, I failed. I walked over to him and said, "That bad?" He said, "Nope actually it was pretty good. You passed!" All items were about 75 percent lower than the max allowable. Just as an example: the HC max allowed was 87 PPM, I had 20 PPM for the 15 MPH test.

Also, " ...I'm more of a practical tech than a theoretical one" I picked up on that, and that's why I asked you. I could/have got the theoretical stuff off the internet and in some of my books, but I wanted someone with the practical knowledge. Again it's greatly appreciated, and to the original poster, glad you got your vehicle to pass.