Help: Failed SMOG - NOx too high
10-07-2006, 01:48 AM
#1
Burning Brakes
Thread Starter
Help: Failed SMOG - NOx too high
Like the title says...my car failed the smog check. Based on the high NOx output (1436 PPM), it seems that I'm running overly lean.
I also have AA chips installed. I plan to swap the chips back to the originals in case the advanced timing is affecting the NOx output.
The car has a good history of passing the smog until now.
I understand that there is a way to adjust the MAF on the 85-86 MY. I would be thankful if someone could tell me where the adjustment is and which way I should turn it to richen the mixture.
Also, if there is any other advice on how I could reduce the NOx output, I'd love to hear it.
Thanking you in advance,
D
I also have AA chips installed. I plan to swap the chips back to the originals in case the advanced timing is affecting the NOx output.
The car has a good history of passing the smog until now.
I understand that there is a way to adjust the MAF on the 85-86 MY. I would be thankful if someone could tell me where the adjustment is and which way I should turn it to richen the mixture.
Also, if there is any other advice on how I could reduce the NOx output, I'd love to hear it.
Thanking you in advance,
D
Last edited by Th Dude; 10-07-2006 at 02:22 AM.
10-07-2006, 02:05 AM
#2
Burning Brakes
To much advance will result in high NOx readings so you may not be lean just advanced due to the chip change. Not well versed on what the AA chips due to know if that is really the issue but I would retest with the standard chips in place.
10-07-2006, 11:44 AM
#3
Rennlist Member
Hello Derek
The MAF idle mixture pot shouldn't affect the idle CO if the O2 loop is working.. Idle A/F should be 14.7:1 due to the O2 loop.
If you think the MAF is so far out that the loop is out of range, then there is a proceedure in the WS manuals. You turn the pot on the MAF clockwise to richen
The MAF idle mixture pot shouldn't affect the idle CO if the O2 loop is working.. Idle A/F should be 14.7:1 due to the O2 loop.
If you think the MAF is so far out that the loop is out of range, then there is a proceedure in the WS manuals. You turn the pot on the MAF clockwise to richen
10-07-2006, 12:16 PM
#4
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Derek--
Do a little searching on your high NOx and you'll discover that a few folks have been through this before.
30-second synopsis:
-- Put the stock chips back in.
-- Make sure the ignition system is in good shape.
-- Make sure the oxy sensor is close to new.
-- Use the original COPPER plugs rather than the platinums.
-- Smog pump should be working.
-- Get the test guy to run the car with the trans locked in gear 2.
-- Make sure the CAT is up to temp when you test.
This combination allowed me to get past the NOx after marginally failing (as you did) a few times.
As a last resort, a new catalysts will clean the car up long enough to pass the test, unless you are just pouring garbage into the front of it. There are some hi-flow cats around that help with performance. I remember seeing some X-pipe & hi-flow cat combinations from a few of our favorite vendors. Certainly worth a look if you need to put a new cat on anyway.
Do a little searching on your high NOx and you'll discover that a few folks have been through this before.
30-second synopsis:
-- Put the stock chips back in.
-- Make sure the ignition system is in good shape.
-- Make sure the oxy sensor is close to new.
-- Use the original COPPER plugs rather than the platinums.
-- Smog pump should be working.
-- Get the test guy to run the car with the trans locked in gear 2.
-- Make sure the CAT is up to temp when you test.
This combination allowed me to get past the NOx after marginally failing (as you did) a few times.
As a last resort, a new catalysts will clean the car up long enough to pass the test, unless you are just pouring garbage into the front of it. There are some hi-flow cats around that help with performance. I remember seeing some X-pipe & hi-flow cat combinations from a few of our favorite vendors. Certainly worth a look if you need to put a new cat on anyway.
10-07-2006, 12:20 PM
#5
"To much advance will result in high NOx readings so you may not be lean just advanced due to the chip change. Not well versed on what the AA chips due to know if that is really the issue but I would retest with the standard chips in place."
You're correct in stating that the timing has been advanced in the performance chip which is
the case for most/all chips as more fuel does little/nothing. You're also correct in stating that
the excessive advance causes excessive NOx at the loaded (dyno) emission tests at 15 & 25 MPH,
especially when the CAT is marginal.
You're correct in stating that the timing has been advanced in the performance chip which is
the case for most/all chips as more fuel does little/nothing. You're also correct in stating that
the excessive advance causes excessive NOx at the loaded (dyno) emission tests at 15 & 25 MPH,
especially when the CAT is marginal.
10-07-2006, 12:30 PM
#6
Burning Brakes
Thread Starter
Cruiser, John, Bob, and Loren,
Thank you for the tips and insight.
I'll swap the chips back.
The O2 sensor is a little over a year old.
Using copper plugs...I'll check their condition...they are only 6 months old.
I'll ask him run the test in 2nd gear and I'll make sure to drive the car a bit before going to him.
The cats are original and I'm approaching 150K miles. If I fail again, I'll look to replace them.
I'll run a search and see if I can find any further tips.
D
Thank you for the tips and insight.
I'll swap the chips back.
The O2 sensor is a little over a year old.
Using copper plugs...I'll check their condition...they are only 6 months old.
I'll ask him run the test in 2nd gear and I'll make sure to drive the car a bit before going to him.
The cats are original and I'm approaching 150K miles. If I fail again, I'll look to replace them.
I'll run a search and see if I can find any further tips.
D
