Took it for emissions, and failed
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Freshman User
Joined: Jan 2006
Posts: 46
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Took it for emissions, and failed
Hey everyone, i took my 351m equiped 78' F-100 for emisions today and failed the NOX part. can someone tell me what exactly NOX is and what could cause me to fail that part? thanks in advance.
Postmaster
Joined: Feb 2003
Posts: 4,043
Likes: 4
What year truck? What emmissions equipment does it have? What size engine?
NOx is Oxide of Nitrogen (not the go-fast happy gas racers use). It is formed from the Nitrogen in the atmosphere combining with oxygen in the combustion chamber. This occurrs when the combustion chamber temperature is high. Could be caused by:
1. Timing too far advanced
2. EGR not operating properly
3. High compression ratio in the engine
4. ????? There are other causes, but I can't thing of them right now.
NOx is Oxide of Nitrogen (not the go-fast happy gas racers use). It is formed from the Nitrogen in the atmosphere combining with oxygen in the combustion chamber. This occurrs when the combustion chamber temperature is high. Could be caused by:
1. Timing too far advanced
2. EGR not operating properly
3. High compression ratio in the engine
4. ????? There are other causes, but I can't thing of them right now.
Posting Guru
Joined: Jul 2003
Posts: 2,222
Likes: 1
From: East Central Florida
Here are a few more causes for being out of parmeters;
Running too lean
Leaking air through a faulty Vacuum line or around the carb base plate,
Bad PCV Valve ot hose to valve
too small a carb or leaky throttle plate shaft. . . .
Usually something really insignificant and seemingly foolish
FBp
Running too lean
Leaking air through a faulty Vacuum line or around the carb base plate,
Bad PCV Valve ot hose to valve
too small a carb or leaky throttle plate shaft. . . .
Usually something really insignificant and seemingly foolish
FBp
Junior User
Joined: Dec 2005
Posts: 89
Likes: 0
From: Glendale, Arizona
Last year my truck failed the same thing on two consecutive tests. It wasn't until I noticed that the only time I was actually failing was during the idle under load test a.k.a. "brake torque"
So what I did was went back home and reset the tune up perameters my truck again. Only this time, all of the tune up specs for my truck were set up while the truck was in drive and while the brakes were activated.
Went back for my third test later that same day and the truck passed every single test with flying colors!
Then the only problem I had was that it took me at least 3 or 4 weeks to retune my carb & relocate that sweet spot that my truck likes so much.
Can't really say for sure if this option will help you out or not? However, what I can say is that this method is certainly a lot cheaper than most others available out there and that it certainly did work for me!
Good Luck
"75 SuperCab"
So what I did was went back home and reset the tune up perameters my truck again. Only this time, all of the tune up specs for my truck were set up while the truck was in drive and while the brakes were activated.
Went back for my third test later that same day and the truck passed every single test with flying colors!
Then the only problem I had was that it took me at least 3 or 4 weeks to retune my carb & relocate that sweet spot that my truck likes so much.
Can't really say for sure if this option will help you out or not? However, what I can say is that this method is certainly a lot cheaper than most others available out there and that it certainly did work for me!
Good Luck
"75 SuperCab"
Senior User
Joined: May 2004
Posts: 113
Likes: 0
We dont have to worry about the VET anymore. They did away with it a year ago.
I always got mine to pass by running premium (93 Octane) a week before I was going to have it tested.
All your vacumn systems must still be working properly though.
I like the way it ran on premium, that all i put in it now is premium. Carb stays cleaner, plugs, less maintenance, better fuel mileage. I am staying with 93 octane from now one.
Chrysler owners manuals all recomend 93 octane premium in their engines.
I always got mine to pass by running premium (93 Octane) a week before I was going to have it tested.
All your vacumn systems must still be working properly though.
I like the way it ran on premium, that all i put in it now is premium. Carb stays cleaner, plugs, less maintenance, better fuel mileage. I am staying with 93 octane from now one.
Chrysler owners manuals all recomend 93 octane premium in their engines.
Postmaster
Joined: Aug 2005
Posts: 2,760
Likes: 8
From: Gadsden Purchase
This won't help Spartan with his NOx problem... I was complaining about the emmisions racket in an autoparts store and a customer offered this...
"I have some of the same equipment they use and if you get that pickup tube over some -used- motor oil the gauges go crazy"
Ever since then I change my oil right before a test and since then been batting a thousand too.
Also having had it fail in the past and taking it to one of the shops right next door they turn the mixture screws all the way in and adjust the idle for 750 to 850 rpm and tell me "not to shut it off while waiting in line to keep the exhaust system hot" was the reason given, the others are obvious and weren't mentioned.
So I do those things myself now, take a tach with me and stop somewhere close by and re-adjust everything just before getting into line and un-do it right after I pass. (I don't live in town or I'd do it at home)
Alvin in AZ (follow the money, it's always about money)
"I have some of the same equipment they use and if you get that pickup tube over some -used- motor oil the gauges go crazy"
Ever since then I change my oil right before a test and since then been batting a thousand too.
Also having had it fail in the past and taking it to one of the shops right next door they turn the mixture screws all the way in and adjust the idle for 750 to 850 rpm and tell me "not to shut it off while waiting in line to keep the exhaust system hot" was the reason given, the others are obvious and weren't mentioned.
So I do those things myself now, take a tach with me and stop somewhere close by and re-adjust everything just before getting into line and un-do it right after I pass. (I don't live in town or I'd do it at home)
Alvin in AZ (follow the money, it's always about money)
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Freshman User
Joined: Jan 2006
Posts: 45
Likes: 0
From: DFW, Texas
I could be completly off base here, but in many states, including my own of Texas, there is NO EMISSIONS TESTING for any vehicle pre-1978 - 1979 emissions equipment. Most younger yahoos of a "mechaninc" put my truck up for emissions, even though my truck is exempt. It fails every time, until I point out I'm exempt, except for horn, brakes, wipers & lights. The younger guys have no idea there are years that are exempt for emissions.
I don't know every state's emission laws, but make sure your truck is not exempt before you go trying to "fix" the trucks failed emission woes.
I don't know every state's emission laws, but make sure your truck is not exempt before you go trying to "fix" the trucks failed emission woes.
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