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Discussion Starter #1
This is on my backup truck, an '87 Mitsubishi Mighty Max, but the process should be the same. I welcome feedback 'cause I'm just takin' a couple of shots in the dark.
The NOX is high in the 25mph test. All other tests passed w/flying colors. The passing of the other tests hints at a good catalytic converter, even tho it's the original. I would like to avoid replacing this, since this will be the last emissions for this truck.
I had fresh plugs, fresh oil, new air filter, and retarded timing when I went for the test. When I pulled my old plugs I noticed they were white, not the normal brownish tan. I'm thinkin' this indicates a lean condition, which is the path I'm taking. The compression is good on all 4 cylinders, 150psi adverage, all within 10% of each other.
I scraped the crud out of the egr not too many years ago, but I plan on checking that. I pulled the head, 6 months before I parked the truck, and scraped a lot of crud off the top of the pistons and combustion chamber. I'm always running high test gas w/maximum timing advance (just under spark knock).
I'm going to put a DVOM on the oxygen sensor to make sure it's working (kinda hope it's not).
I'm also going to run one or two tanks of gas w/an additive in it, mainly to clean the carb jets, since the truck sat for 8 years. Either Lucas Deep Clean or Seafoam. Not totally sold on the Seafoam, so I'll probably go w/Lucas first.
So, that's where I'm at while I'm waiting to get my '01sc into the garage for head gaskets. Always something major with the Nissan. Last 3 years running. Always at Christmas time.
I'll be posting w/progress on the '01 when I get to it. Anybody have any more thoughts on the failed emissions. I need to get to work w/this truck and I'm running Nissan plates on it right now.
 

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Since it's NOX, it's most likely bad/clogged egr valve, or a cat on the way out. If the other two gasses are much lower than your states limits, try retarding the timing and or richening up the mixture(if carbed) a bit. The higher you get the HC and CO, the lower the NOX goes.
 

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Discussion Starter #3
Pretty sure the AF mixture screws are sealed, but I'll take a look. I've got plenty of room to play as far as the other readings are concerned. Had the timing retarded when I tested it. Thanks for the feedback. I'll keep you posted.
 

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Discussion Starter #4
Well, I failed the freeby test. Still high nox @25mph. All other readings well within specs. What I did before this test was to run a can of Seafoam in the fuel tank and fill up w/high test. I also replaced a bad o2 sensor, retarded the timing, checked the function of the egr (working good), and changed the oil. The nox readings were actually higher.
BTW, when I went to buy an o2 sensor I first went to Auto Zone. They wanted $38, special order and prepay, and wouldn't guarantee it if the wire was cut and the unit was bad out of the box. Went to Advance Auto and they had one in stock for $18 and would cover under warranty for 1 year w/the wire cut. So much for AZ.
Anyway, my next plan of attack is to buy some colder plugs (since nox is connected to combustion temperature). Maybe 2 steps colder. Pull and clean the egr. Fill up w/Chevron high test (instead of Sheetz) for 2 tanks. Change the dist. cap and rotor (long shot) and test on a rainy day.
That's all I've got. Hopin' the cold plugs get me thru. Anybody have any more ideas?
 

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Discussion Starter #5
Well, I went the long way around. Failed 3 times and my Frontier tags are expired. Cleaned the egr passages (lots of goop in there) but that didn't help. Seems like everything I do to improve emissions makes it worse. Finally broke down a put a new cat on it ($145). Passed w/flying colors. :) Gettin' tags on Monday. Time to get to those heads on the '01 sc.
 

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Sucks to have to spend that on a truck it doesn't sound like you are keeping but good you got it fixed. Emissions testing sucks!
 

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LOL, nova. we dont have that crap here. my last 2 cars didnt even have cats and my inspection consist of a light check, horn, and a look at the tires and wipers(if the guy feels like it). move a little farther south and you wont have to worry about emissions.
 

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Where are you from? Our surrounding cities outside the Dallas-Fort Worth metroplex don't have to do this but in Dallas and Tarrant county they come down on us hard. The last time I failed an inspection it was because I was missing four lug nuts from removing the locking lugs. There is usually a cop parked across the street waiting to pull you over and preform his own inspection. Bastards! I lived in the small town of Greenville, TX for a while and there they would inspect my truck that didn't have a cat, exhaust dumped right after the cab, no interior, one seat that wasn't even bolted down, and was too low to meet any law in any state. The more beer you bought them the more you could get away with.
 

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Discussion Starter #9
Sucks to have to spend that on a truck it doesn't sound like you are keeping but good you got it fixed. Emissions testing sucks!
Oh, I'm keeping the truck. I've had it since new, it's just a rat now (worked it hard over the years), but its earned a place in the driveway. It's just that this was my last emissions before I'm exempt. Now that I'm passed I can pull the cat off. Time to get to the Nissan garage queen.
 

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Oh sweet that you get exempt! Those are damn good trucks and I would keep it too. It was from Mitsubishi before Dodge ran them into the ground.
 

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Here is a few things I've done to pass before with problems with NOX.

* Go very early in the morning. The colder the better. Avoid driving and engine being heat soaked prior to your test.... heck you might consider showing up a bit early and letting it cool before the test.
* Run 93 octane for a couple of tanks. Will help with any detonation in conjunction with your timing reduction you've done.
 
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