HELP... failed emissions on high NOX

[channer]

Hi All

I need help... I failed emissions test on high NOX using a TurboTweak 36lb emissions chip!!! FP was set to 38psi off according to Eric's instruction.

driiving 2525 test
HC (llimit - 90) - 81
CO (llimit - 0.50) - 0.03
NOX (llimit - 979) - 1878 <-- failed


curb test
HC (llimit - 300) - 70
CO (llimit - 1.50) - 0.01

I just checked the EGR and the motor stumbles when I press the EGR. The 3" cat does is not plugged... and it is the same cat that passed the test 2 years ago when the 150k motor was still stock.

I'm going to put in another EGR and a friend's cat just in case.

What else can I check for!!!!! The new motor (2000+ miles) is slightly modded with ported upper & lower intake, power plate, 62mm TB and some headwork.

I checked the website & most response to high NOX is the EGR system. Beside the EGR valve... what else can I check for, how this the EGR system work!!

thanks in advance.... dave

 

[Royal-T-Ltd]

Usually if you squeeze the EGR and the car stumbles the EGR is GOOD. try lookin somewhere else. Do u have a scan tool? What is you Block learn and intergrator? When did you last change your O2 sensor? how bout your plugs? Check for vaccum leaks, cracked header?

 

[channer]

When I took the car in to get checked... the BLM where 112, didn't check the O2 counts but most of the time it hovers around 500+ @ idle. The TPS=.42, IAC=20, INT=128. I couldn't get the BLM to 128.

I changed oil & plugs (cr43) and no header (ATR) leak that I know of.

I don't think I have any vacuum leaks... is there an easy way to look for vacuum leak?

Is there any other way to check the EGR system out?

dave

 

[Mac in SD]

Pssst. Put a couple of bottles of Heet in the tank. NOx go away.

 

[Royal-T-Ltd]

You can cut a piece of gasket material the size of the vaccum distribution block on top of the upper plenum [except dont cut any holes... just the 2 so screws pass through] this will essentially eliminate chances for external vacuum leaks.... if your BL goes closer to 128 at idle then you have a vacuum leak. if it does not change you are fine [115 isnt that bad of a number but is on the rich side] ACTUALLY YOU DONT HAVE A VACUUM leak im trippin... i just noticed you said your BL was 112... a vacuum leak would cause your BL to go up becuz it was causing a lean reading[>128]. Soooo you can adjust the fp and watch the BL at idle / reduce it and see if it goes up. then you can also put in hotter plugs [when emissions time rolls around i swap in my 45ts, and if all else fails you probably need to have a cat strictly for the emissions test... when you pass, take it off, i had a 3" cat which passed the first year, after years of racing it doesnt work any more... now my brothers and i share an emissions cat [a 2" autozone cat modified for t-types] HTH keep me posted

 

[channer]

Royal-T-Ltd...
- thanks for the suggestion on checking for vacuum leaks. I'll do that since I am replacing my EGR valve this weekend

Mac in SD
- thanks for the recommendation. How many bottle should I use? Is this going to offsite any other number (CO & HC)


thanks again.... dave

 

[Mac in SD]

Check your PMs.

 

[gofstbuick]

The egr passages may be clear, but is the ECM commanding the EGR solenoid? Are you getting a vaccuum signal to the egr valve while the car is moving down the road? What kind of cam are you running and who's chip are you running. Does the chip maker command egr of is the egr solenoid bypassed. By the way, if you use hotter plugs, is takes more energy to fire the plugs, thus the spark is hotter and NOx will rise. Since your HC is high at idle and CO is low at idle, you might be just a tad bit lean. Waht are the O2 readings on the emissions test? Higher than 0.3% at idle, then you are either lean or your cat is bad.

 

[channer]

gofstbuick

I was using TurboTweak's bluetop emission chip and the EGR setting is active. The FP was set at 38 off-line.

I changed the plugs from cr42 to cr43 for the test. Should I go back to CR42? There were no O2 reading during emissions. The O2 at idle are normally around 500-700. My BLM during the test was 112... I could get it to 128.

I don't know anything about the cam but it's probably a little hotter than stock.

As for the 3" cat... I took it out and it looks ok. It's the same cat that pass NOX @ 35 ppm (1164 limit) on a 150k stock motor two years ago!!!

What is the best way to get the motor to run a little richer?

dave

 

[Royal-T-Ltd]

Why are you trying to get the car to run richer? - Also just because the cat past 2 years ago doesnt mean anything. read my post again.

 

[gofstbuick]

Replace the CR43 with CR42. The reason for a little richer is that the extra fuel will cool combustion temps and reduce NOx. He has some room to richen the mixture. If you look at a stiochiometric graph of the 5 gases (HC, CO, NOx, O2 and CO2) you'll notice that NOx is low during rich mixtures and increases as the mixure gets lean and then drops off again once the mixture reaches the point of lean misfire. The reason for the reduction during lean misfire, is there is not enough energy being produced to create the temperature to induce NOx, because there is not enough fuel to fire.

 

[Hacksaw]

For my $.02, focus now on:

1. The O2 sensor. The cycle time gets slower as they age, and they can go rich or lean as well.

2. The EGR passages being clean. Yes, it might stumble when you manually activate it, but if the passages are gummed up, too little EGR flow will cause high Nox. And makes EGR comes on above idle. You could tee in a vacuum gauge into the EGR vacuum line & watch it as you drive around. Some ECM chips turn off EGR all the time, but since that is supposed to be an emissions chip it sound not do that.

3. Carbon in the engine? Yes, the motor is fairly new, but there may have been some carbon build up during break in as it used oil. So, run something like GM's Top Engine Cleaner to be sure.

 

[its turbo time]

Pssst. Put a couple of bottles of Heet in the tank. NOx go away.

that works so well its almost magical...my old 85 ran like a donkey and it passed with flying colors