help on emissions - failed test

[channer]

Hi All

I need help ... I failed emissions test on high NOX using a 36lb emissions chip!!!

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 tested the EGR & the motor stumbles depress the EGR valve, I took the Cat off and it looks fine.

What else can I check for!!!!! Is there anything else from the test results that could point to something else? The motor (3000+ km) is slightly modded with ported upper & lower intake, 62mm TB and some headwork.

How can I fully test the EGR system to see if it is functioning as it should?

thanks in advance.... dave

[GNxwannabe]

Emission testing in the Illinois do not pass/fail for NOx.
I believe that a Lean tune will generate higher NOx. I wonder if your
emission chip is calibrated in such a way to get lower HC's.

My car ran horrible with an emission chip. I tested using my Extender
chip and passed no problem.

When the EGR fails you'll know it. The car won't idle correctly.
It might be worth trying your street chip and set the FP accordingly.

Good luck

[channer]

The 3 bluetop chips (JC, RA, Thrasher) that I have run rich at idle... so I don't think they are passible. That is why I opted for an emissions chip to pass. I was thinking about throwing in my stock injectors and chip and see what happens

Is there a way to check if the EGR system is blocked? Would it still run rough if blocked.

dave

[Robert Walton]

Originally Posted by channer

Is there a way to check if the EGR system is blocked? Would it still run rough if blocked.

#1 you already checked the EGR ports. By lifting up the valve by hand and the car stumbled/died the port is open.

#2 lift up the valve. Remove the vacuum line. Put your finger over the nipple ( ) of the EGR while holding it up. If the valve staus open the diaphram is good.

#3 put a vacuum gauge in line with the EGR. Use a Tee. Go drive it. Do you get vacuum at at steady state cruise? If so, the computer,chip, and EGR solenoid are all working

If the test above all pass then the EGR system is not the problem.


A catalytic converter will flow fine and look fine but not work fine. We use a number of things but an infared temp gun usually works best. The outlet should be a minimum 100* F HOTTER than the inlet of the cat at 2500 rpm.


Looking at your numbers I'd look at the EGR valve first. GM is notorious for popping diaphrams. If you decide it is the valve itself that's bad PLEASE buy a GM part. The part number is stamped on the top

Good luck. Maybe you should find a "buddy" shop that'll "test" it for a little extra "gratuity"

[channer]

Robert

thanks for the response. I will perform the other 2 EGR test. I've got another EGR from a friend but I was thinking about buying a new EGR anyways.

Would porting/eliminating the EGR tower in the lower/upper intake skew the numbers? How does the EGR system work... there is the EGR valve that opens/closes... somewhere, gases get passed from the intake to head or vice versa!!!

Well, I've been looking around for a "friend of a friend"... but a number of shops got busted recently doing "magic passes" so I think everyone is laying low right now!!!

thanks again... dave

[Robert Walton]

Originally Posted by channer

Would porting/eliminating the EGR tower in the lower/upper intake skew the numbers? How does the EGR system work... there is the EGR valve that opens/closes... somewhere, gases get passed from the intake to head or vice versa!!!

I don't know about porting the intake. I would think that as long as the hole is still there it wouldn't change anything.

There are some little slots inside the exhaust port that are connected to the intake side. The EGR valve sets on top of these two ports. Take the valve off and you will see what I mean. One side will be all black and carboned up,that is the exhaust side. The intake side is just vacuum.

There is a solenoid that the computer turns on/off. This controls when vacuum gets to the EGR valve. You should ONLY have EGR at part throttle cruise. Idle or WOT no EGR.

EGR introduces spent exhaust gasses back into the intake as a way to cool down the combusion temperatures. This will help lower Nox.

NOx is always a product of heat. Yes some will say a lean mixture will cause NOx. Look at your other numbers though. They are good. High speed HC is a tad high but that is an indicator of fuel mix. Drop the fuel pressure a lb. or 2 to fix that.

Remember the converter does a huge part in reducing NOx.

Again good luck. BTW, it is currently 75*,blue skies,slight breeze here in Houston. What's winter like in Canada? Sorry had to do that. Have a Labatt on me

[channer]

HI Robert

Thank you again for all the info.

it was sunny & probably 65-70 today, and tomorrow is suppose to be partly sunny/rainy and 65ish. To be "politically incorrect"... we are having an extending Indian Summer. Last year at this time, we were probably in parkas & boots... brrrr!!!

Since it will be somewhat nice & warm this weekend, I will be working on my car and having a few Labatts!!!

thanks again... dave