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Topics regarding exhaust systems beginning at the headers down the pipes and through the catalytic converter and the mufflers and exhaust tips. We can also discuss emissions, performance cat back exhausts, or any exhaust related topics.
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fail my smog check....need help lowering my NO (PPM)

October 18th 2014, 9:00pm

Hi everyone,

need some help wondering if anyone can help me or tell me how i can lower my NO (PPM) I did not pass at 15mph , but I did pass on 25mph. Not sure how this works.

see results below:

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Re: fail my smog check....need help lowering my NO (PPM)

October 18th 2014, 9:17pm

What's your tune up history.

Last time you used injector cleaner.

New air cleaner.

PCV valve.

Spark plugs.

Oil change.


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Re: fail my smog check....need help lowering my NO (PPM)

October 18th 2014, 10:06pm

oil change about a month ago
spark plugs haven't changed in a while probably since 2012.. yikesss :(
air cleaner haven't changed in probably one year or could be two. yikes lol
pcv valve still the same..

i've been reading that i should clean my EGR Valve and change my air cleaner... perhaps? a change of spark plugs woulnd't hurt? hmm.....

never used inject cleaner. ;(

Re: fail my smog check....need help lowering my NO (PPM)

October 18th 2014, 10:25pm

If you have never used injection cleaner, shame on you. Shock the injectors with a slight overdose of Lucas' Injector Cleaner.

Then take your truck out on the hi-speed super slab and kick it in the but for a while. If that doesn't help, you may be looking

at a tune up, and possibly a new catalytic converter to clean up the mess. It is possible that the engine has been running rich

and killed the cat. (I had the same problem several years ago.)

Good hunting

Uncle Bob

Re: fail my smog check....need help lowering my NO (PPM)

October 18th 2014, 10:30pm

Air cleaner and EGR are a yes to service.

Fuel system cleaner and rub it hard. It is common knowledge a car should be run hard and cleaned out before a test. At least a 1/2 hour on the freeway. Some quarter mile runs really help. Changing the plugs may help some but it don't get the carbon out of the head and off the piston. Which causes higher compression. Which in turn causes higher NO readings.

Re: fail my smog check....need help lowering my NO (PPM)

October 18th 2014, 11:17pm

chevymaher wrote:Air cleaner and EGR are a yes to service.

Fuel system cleaner and rub it hard. It is common knowledge a car should be run hard and cleaned out before a test. At least a 1/2 hour on the freeway. Some quarter mile runs really help. Changing the plugs may help some but it don't get the carbon out of the head and off the piston. Which causes higher compression. Which in turn causes higher NO readings.



oh ok then will change air cleaner and of course will take off egr and clean it real good...i will get one of those fuel system cleaners and run the van for a bout a 1/2 hour see if that owrks.

Re: fail my smog check....need help lowering my NO (PPM)

October 18th 2014, 11:18pm

RECox286 wrote:If you have never used injection cleaner, shame on you. Shock the injectors with a slight overdose of Lucas' Injector Cleaner.

Then take your truck out on the hi-speed super slab and kick it in the but for a while. If that doesn't help, you may be looking

at a tune up, and possibly a new catalytic converter to clean up the mess. It is possible that the engine has been running rich

and killed the cat. (I had the same problem several years ago.)

Good hunting

Uncle Bob


my catalytic converter is brand neww bought it two years ago, but i will clean my EGR valve change the airfilter and of course run a injection cleaner on it.

Re: fail my smog check....need help lowering my NO (PPM)

October 19th 2014, 12:51am

CargoCrawler taught me a neat trick. Keep a new gas cap, air cleaner, preheat snorkel hose, fuel filter, stuff like that, in a clean spot. A couple weeks before your smog check, put on the new stuff. Clean the injectors. Run it around the freeway. Then get your smog.

Mine is every 2 yrs so I just plan on replacing all that stuff every other year. The air cleaner I change more often, of course. The gas cap I keep for the smog check then put the old one back on unless the gasket looks weird.


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