Its a 86 TPI Camaro, 165 ECM, stock 305 except for 180° t-stat, headers, new 3" catalytic converter, 3" cat-back, and mildly ported plenum.

My car is failing the NOx by quite a bit, but it passes HC and whatever else is tested. I have read that high NOx may be caused by high combustion temps, so my guess is that it's either running lean or too much spark advance. Could that be right?

What would I be able to change in order to lower my NOx emissions?

I just got an AutoProm today so my first efforts in tuning will be to become familiar with it and to pass emissions.


Thanks for ANY help!

 

I thought they banned the E-check last year dude?

 

well as far as i know, only 9 or so countys still do it, and im in one that does. but last year they made it free, it used to be $20. so for the time being, im stuch trying to pass

 

too lean can be a cause of high NOx, what is the standard & what did your car produce?
also, if tested, what were the CO, HC, CO2 & O2 readings?

pulling some timing in the bin can help. make sure base timing is right before changing it in the chip. if you pull too much it can hurt in other areas.
EGR is the main component in NOx reduction, so make sure your EGR valve is working & has an effect on the motor.
some vehicles don't turn the EGR on at the low speeds run on a dyno test, check what the speed is set at in the bin.

 

You can also try a quart of Denatured Alcohol in a half tank of gas. Worked great for me on 2 differnet vehicles - one of which was 95 F150 with 275K on the clock and the original cat with the engine never having been opened. Other car was the 383 in my sig....

 

My truck passes with theoreticly ( impossible ) perfect numbers across the board.
Since they made it "free" it took a couple trips, but it didn't cost. Told 'em I'd got it looked at, and needed checked again. The balked, but ran it.
I'd pull timing in the test range, and run it through again.
Unfortunately, they don't report NOx if it passes, so I really don't know what that was.
My latest only reports 0% CO, 15.43% CO2, 0% HC, and 28 PSI gas cap pressure ! PASS
There's no EGR on the motor at all, but they can't recognize the difference between a Chevy 350 and a Buick 455 anyway, and since it passes....

 

im kinda glad you brought this thread back up, tomorrow im planning on going to echeck again, planning on passing but hey... ya know... haha

since last i failed, ive gotten the APYM (89 305 w/ auto) running in my 86 Camaro. Im hoping the $6E vs. $32 will help. Should i expect it to?

Also, my car was running very lean, and failing NOx, which makes sense. I dont have the numbers that it failed by right now. I have tweaked the injector constant and have most part throttle areas within about +/- 6 BLMs of 128, not great from what ive read but it is atleast centered at 128 where it used to only be high.


So, if i pass by going to $6E and adjusting the injector constant, I'll report that back int his thread, jsut incase someone stumbles upon the thread in the future.

 

Do *I* think a $6E will help ? No, not at all.

*I* think that the mill is burning what it's burning, and what it's burning is going out the tail pipe and into the sniffer. What affects what gets to the sniffer will be the fuel, spark, and the cat.

Now, take the rest of this in context of this thread, Ohio E-check.

My BLM's on the 7747 range about 118 to 140 or so. On the 8746 stays 128 no matter what, and the INT ranges about 90 to 135 or so, slightly rich. Tells me that my fuel tables are as close as I'm gonna get 'em, or close enough to not care much. Tells me that the 7747 is more "dynamic" about sliding BLM's by the second ( no delay in the 7747 ) but within the ECM's ability to "correct" back to 14.7 AFR, as far as O2 goes anyway.

What I believe, is that if the BLM isn't banging its little pointed head on the limits, then the ECM is correcting to 14.7 AFR, so that is not affecting the sniffer. The ECM has "fixed" that as far as the test is concerned. If it *is* hitting limits, then fuel is out of range, and will likely fail the test. ( and light the check engine light )
Late spark will reduce NOx and increase HC. ( and cause an O2 to give false readings ) Seems like you can afford that for the test, which is why I said pull spark in the test range.

For me, and what I did, FIRST get past the test, then file that bin for next year. Go buy license plates, THEN make it run right. After it's running right, ( with good plates ) THEN go through the free test again. They won't take your plates away, so you can continue tuning even if it fails this time.
O2 sensors have their problems. Everyone on this site seems partial to wide band, except me. I bought an exhaust gas analyzer off ebay. It's uncalibrated, but I have a friend with a 5 gas, so we're gonna fix that. Only worth anything pre-cat, so had bungs added just for it.
Even after all of that, if the cat is good ( I just incinerated two of them last week ) and the fuel is within the range of the ECM to correct, then it should pass. If the cat is bad, then the tune becomes hyper-critical, and it's easier and cheaper to buy a new cat. $185 at my favorite exhaust guy here ( no, not me ) but still possible to pass E-check if the tune in the test range is PERFECT.
If I were you, I'd stay with the $32 until you pass the test. You already know why the $32 failed, but you don't have a clue if the $6E will pass, or fail, or why.
I'd fix the problem I know, rather than risk a bunch more problems I don't know.
AFTER you pass the test, and get plates, then do whatever you want.

Just my opinion, ya unnerstan...

 

I appretiate the effort in your reply! Forgot yesterday was the 4th and they were closed, so I hope to make it today. I was thinking about sticking with #32 for the test then using $6E, but with $6E its running with closer BLMs and has a smoother idle, so I feel pretty good about using it. The cat is newish, the O2 sensor is about 1 year old, just ran some injector cleaner through... so if it does not pass then ill have to do some head scratching..

Also, with the $32 orginally the BLMs were about 160, which i think is the limit it had set, so I believe it was lean to the point that it could not correct. Fixing that alone I believe will allow me to pass.

Like I said ill post back if thats what fixed it.

thanks.

 

So, How'd it go ?

 

Thanks for bringing the post back up, I just got back from a vacation a few days ago and almost forgot about it.

My car did pass the e-check. all numbers where quite low except the NOx which only passed by a little bit. but still passed.

My own conclusion is that changing the injector constant made teh most difference, as it brought the BLMs closer to 128 rather than being maxed at 160 lean. BLM would hit 160 and the A/F ratio correction was over, when it still needed more fuel added.

Also I set it to have the TCC lock at the 25 mph test speed, hoping that it might run a lil lower RPMs, thus spitting less out the tailpipes. Never actually checked how much lower the RPMs would be so I cantg say that it helped or not.

 

Spitting less TOTAL out the pipe, but that's not what they check for !
They look for %, or parts per million. Same thing, pretty much.
Nigh NOx suggests too much advance, not enough EGR ( I don't run EGR at all ) or running lean.
Since everything else is low, I'd suspect too much advance.
Run it on your favorite dyno ( road, hill, whatever ) then back off a couple degrees, and run it again. Keep backing off until you see performance drop, then undo the last move.
Go run through the free check again.

 

well i did pass atleast, so i dont think ill go back for another test. the timing is untouched by me so far, its the stock timing or an 89 305 f-body. by saying that its still stock timing im not saying its good by any means haha, just that i havnt bumped it up. after i get the BLM fueling ordeal better set, ill be doing a lot more reading and playing with spark.

thanks for your suggestions and such.

 

locking the converter probably contributed to the NOx.

i have found that many cars that won't pass with the shifter in drive so the trans can shift will pass just fine if i hold it in a lower gear. my car has problems passing both the low & high speed tests in second gear, but it passes in first with no problem.