Help!! Cant seem to make it pass smog. (1 Viewer)

RodrigzCrzr

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So I have been through and through with the emissions book and checking everything.
I did find a vacuum hose connected to the wrong port. Still can’t get the NOx down.
Input needed.!!
What am I missing?

B843A2C5-F758-46A1-9FCA-99F3AB8F3B23.jpeg
 

Spike Strip

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High NOx can be from mix too lean or high combustion temps.

Did you put something in the Gasoline?

EGR working?

Timing too advanced? (you can have it retarded 2* and still pass).
 

RodrigzCrzr

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High NOx can be from mix too lean or high combustion temps.

Did you put something in the Gasoline?

EGR working?

Timing too advanced? (you can have it retarded 2* and still pass).
No I didn’t put anything in the gas tank.
From testing the egr over and over it showed it was functioning.
 
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Had the same problem a few years ago. Here’s my post from back then when I finally passed.

You have low O2 and that might mean you have the same problem I had- no air injecting into the exhaust. Read through that post and DM me if you want to jam on it.

Oddly enough I think I went to the same exact Smog station you did when I first bought my truck!
 

RodrigzCrzr

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Had the same problem a few years ago. Here’s my post from back then when I finally passed.

You have low O2 and that might mean you have the same problem I had- no air injecting into the exhaust. Read through that post and DM me if you want to jam on it.

Oddly enough I think I went to the same exact Smog station you did when I first bought my truck!
Hey Frickre
Thank you for the reply. I have read your thread several times since I have been doing this.
 
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Your HC is really low for the limits allowed. Richen it up a little, retard the timing to factory or a little behind. The idea is to cool down the fire a little. How is the carbon buildup in the combustion chambers? You have to be careful when you remove the carbon that you don't hurt the CAT but you can do a pretty good job with an upper cylinder de-carbon fuel additive or just by using a product like Seafoam or sometimes just with water but you have to be careful.
 
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Do this and you’ll test cleaner than a Prius.
 

OSS

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The combustion temperature is too hot. Almost every tech never checks the timing on these cars.
If yours won't, retard the timing a few degrees and swap the vacuum hoses going to the vacuum advancers on the distributor.
 

RodrigzCrzr

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The combustion temperature is too hot. Almost every tech never checks the timing on these cars.
If yours won't, retard the timing a few degrees and swap the vacuum hoses going to the vacuum advancers on the distributor.
He actually did Check the timing!
He told me the same thing after I tested. “What he would do”
 

OSS

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if denatured alcohol is added to the fuel prior to smog testing, the NOx spewing out of the tailpipe will be higher.
Alch will lower CO at the expense of raising NOx
 

DFXR

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Are you absolutely positively sure that your EGR is working right? I had numbers really similar to that a couple tests ago, when I forgot to take a little BB out of the vac line from the EGR vac modulator to the top of the EGR valve (long story). Low HC, low CO, residual O2 around 1.5, etc. But NOx in the 2300 range. So I tested vacuum on that line and suddenly remembered what was in there. Pulled it out and passed. HC and CO came up a little but not enough to fail.

I know you have checked and checked but this is just my hunch.
 

RodrigzCrzr

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Are you absolutely positively sure that your EGR is working right? I had numbers really similar to that a couple tests ago, when I forgot to take a little BB out of the vac line from the EGR vac modulator to the top of the EGR valve (long story). Low HC, low CO, residual O2 around 1.5, etc. But NOx in the 2300 range. So I tested vacuum on that line and suddenly remembered what was in there. Pulled it out and passed. HC and CO came up a little but not enough to fail.

I know you have checked and checked but this is just my hunch.
I am going to triple and quadruple check again.
 

Spike Strip

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Save your money on the Dyno. Buy a good A/F meter. Weld, or have welded a bung in the downpipe, and save yourself countless hours trying to troubleshoot this crap.

Your numbers are so close, I think just a slight tweaking of the mix and timing would probably do it.
 

RodrigzCrzr

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Save your money on the Dyno. Buy a good A/F meter. Weld, or have welded a bung in the downpipe, and save yourself countless hours trying to troubleshoot this crap.

Your numbers are so close, I think just a slight tweaking of the mix and timing would probably do it.
Would that be installed after that air injection pipe? Or before?
 
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A trick I used to use when we had aircare in vancouver bc and my truck failed, was to buy a couple of gallons of methyl hydrate and pour it in the tank when it was about 1/2 full. Go directly to the test site and test it again. They might be smarter in california about emissions but the hydrocarbon count went waaaay down.
 

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