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High NOx emissions


Old 09-14-2011, 11:48 PM
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High NOx emissions

Im going to Wyotech is wyoming and we recently learned how to do the IM 240 test. Well when i tested the emissions on my truck I had higher than normal NOx. All other emissions were in level so I know its not from running lean. My next two guesses are that my EGR may be a little dirty and isn't functioning properly or my cats are on their way out. My first thing to check is the EGR and I'm wondering what I should use to clean my EGR and how to do it and get it cleaned? I searched for some sort of write up on here but I couldn't find one.

Thanks for your help in Advance.

My truck is a 2001 5.4 Supercrew. 150,000 miles on it and no driveability problems. mileage is great also.
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Old 09-15-2011, 01:21 AM
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To keep it short, I have a question about the use of IM 240 testing on 97 and later Fords running OBDII.
The Ford system used to keep NOX low is done with the EGR system.
This function is controlled by the following, engine rpm, road speed and light throttle application usually in OD or it's possible in third gear under the right conditons.
Does your test procedure force the OBDII system to go into the EGR function?
If not, you may see NOX levels considered to high at a point it's considered legal.
Below this point and at heavey throttle the NOX will be higher with only the cats to offer any clean-up.
Your truck has OBDII that looks at all systems for passing self tests according the PCM program that never changes.
If you have no codes set, the truck is legal per the EPA.
Before you begin replacing parts or doing service on a system with no codes, be sure your not being misled by your testing because the only way you have of seeing any change is by your testing.
Remember, the rest of the world does not have any testing facility and has to rely on OBDII as supported by the EPA as good enough.
Good luck.
Let us know.

Last edited by Bluegrass; 09-15-2011 at 01:37 AM.
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Old 09-15-2011, 01:41 AM
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I dunno - I think California does a lot more than just read out the OBD2 when they do smog checks.
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Old 09-15-2011, 02:05 AM
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I'm sure your right.
No wonder they are broke from going over board with everything.
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Old 09-15-2011, 02:11 AM
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Just had my truck smogged for registration renewal ...

Tailpipe sniff test at 800 and 2300 PRM (CO2, O2, HC, CO)

Funtional tests: EGR and Gas Cap

Visual Inspection: PCV, EGR, O2 Sensor, Fuel Evap Controls, Spark Controls, Wiring to Sensors, Fuel Cap, Cat Converter, Fuel Injection, Vac Lines sensors and switches, Malfunction Indicator Light.

I forgot to ask the guy if he connected to OBDII, but I'm sure he did.

He told me that at the state run classes on performing smog checks, they are taught to look especially close at trucks equipped with additional gauges ... most likely the vehicle is modified.
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Old 09-15-2011, 02:48 AM
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They perform these tests on a dyno to simulate actual driving. Also I think they allow 2 monitors to be not ready. Plus almost all test stations are test only, they can't make any adjustments on site or even recomend a shop. Freaking Peoples Republic of Kalifornia......anybody want to buy a used Govenor?
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Old 09-15-2011, 02:36 PM
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I know it's not part of the post but the people keep voting in the political "LEFT" so these things keep going on and on.
Ca. even mandates special fuel formulations.
First place the price per gallon goes up and goes the highest over time when there is a crude oil supply problem is yet again CA.
As many know, the auto companies even have to provison vehichles with special added equipment specs and PCM tunes to be sold in that state.
Take a look at the cat converter CA. law. Very tough and somewhat rediculas on some of the requirements.
They even tell you limits to the placement of a cat in inches from the original location.
What the cat ID shall be, how big the letters will be and how far away it can be read.
Magnaflow is the first aftermarket mfger I have saw that got it's foot in the CA. door to sell it's cats.
If you want to link to the CA law and see this atrocity, go to the Mag website and follow the link to the CA. law.
You will laugh at parts of the law but to the people who live there, it's no laughing matter.
Last price for OEM right side (one side) cat complete assembly here was well over $1300.
All of their laws are designed to keep tight control over what you do with your property, and trying to make a 'utopian' land to live in.
As much as the last CA. gov tried, he could not get cooperation from anybody to change some of the foolishness that has taken place.
So now the state is bankrupt from all the stupidity and will be looking to the rest of the country's taxpayers to bail it out.
Some how I thnk this [is related] to owning a vehichle and what happens with it's ownership and cost in that state.
Good luck.

Last edited by Bluegrass; 09-15-2011 at 02:39 PM.
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Old 09-15-2011, 04:33 PM
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As far as the test i did at school. We have a dyno that we put my truck onto and did a simulated road test. we did a complete drive cycle to make sure all the monitors ran. I got the emissions part of that by putting in a probe in my tailpipe. This was my first experience with this certain test, but we also performed it on a 98 explorer and a 06 dodge charger. Those vehicles did passed and my truck was the only one with higher NOx levels. During the test we ran the truck at cruising speeds and i monitored the EGR to make sure it came on. It showed that it opened. That made me think that the valve may not be opening all the way which could lead to slightly higher NOx.
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Old 09-15-2011, 05:46 PM
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Very good.
You have run across a situation when your testing is at a location point that can see the end result the OBDII could not resolve as a fault.
Look closely at the possibility the intake manifiold ports behind the EGR are restricted with carbon buildup.
The PCM never actually measures the NOX because it's not equipped to do that.
What it depends on is self testing the 'engineered' system that is supposed to allow the motor to meet the nox standard.
It does this by testing hardware operation and it's measured flow function as read by the DPFE sensor. This reading by the DPFE is compaired to a narrow range of values in a table within the program for a pass or fail decision.
The cats should finish the job but is at a location that cannot be tested unless it's done by a procedure such as you have access to.
Great learning tool you have to work with.
Good luck.
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