Emissions woes....
Thread Starter
Advanced
Joined: Mar 2010
Posts: 72
Likes: 1
From: Phoenix AZ
Emissions woes....
So I have had the 95 Vette for 5 days now, and for the last 3 of those it's been in the shop due to a failed emissions test. Car has 45k miles, SLP intake, shorty headers, high flow cats, x-pipe, roller rockers, and MSD ingnition. Car runs like a champ, and got phenominal milage on the drive back to Phoenix from Las Vegas.
Car passed all tests with flying colors with the exception of the NoX portion. According to the shop the cats test good, EGR system tests good, they serviced the injectors, and the car failed once again for Nox. They started the tuning process (not a performance tune, just a tune to try and get it to pass) Two days of this and still no luck. At one point they got it to pass Nox, however it then failed CO.
I guess I am really just venting at this point as the car is in what I think are good hands. Shop had great reviews on a local forum, and the customer service has been top notch to this point. But if anybody has any bright ideas they would like to share I am all ears!
Car passed all tests with flying colors with the exception of the NoX portion. According to the shop the cats test good, EGR system tests good, they serviced the injectors, and the car failed once again for Nox. They started the tuning process (not a performance tune, just a tune to try and get it to pass) Two days of this and still no luck. At one point they got it to pass Nox, however it then failed CO.
I guess I am really just venting at this point as the car is in what I think are good hands. Shop had great reviews on a local forum, and the customer service has been top notch to this point. But if anybody has any bright ideas they would like to share I am all ears!
Instructor
Joined: Feb 2010
Posts: 217
Likes: 0
From: Sherman Oaks CA
Wow I did not realize AZ smogged. I lived in Tucson back in 2002 and I dont remember having to smog my truck?
Are you getting any codes thrown ?
You may have a partially plugged exhaust passage that feeds the EGR valve. Also try replacing the oxygen senor with a new unit. Sometimes a plugged or semi plugged cat can throw off NoX reading.
Are you getting any codes thrown ?
You may have a partially plugged exhaust passage that feeds the EGR valve. Also try replacing the oxygen senor with a new unit. Sometimes a plugged or semi plugged cat can throw off NoX reading.
Last edited by dirtcheap74; Mar 19, 2010 at 01:02 AM.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
maybe the cam is the problem............wonder if you tried a set of 1.5 rockers to detune the cam? a set of $45 stockers might just get it to pass. Then reinstall your 1.6's and in 2 years............
Safety Car
Joined: Jan 2004
Posts: 3,783
Likes: 15
From: Northern California
The free flowing exhaust (headers, cat & x-pipe) are contributing to a Lack of Exhaust Back Pressure which the EGR valve needs to operate correctly.
Re-install the stock exhaust components and with the added back pressure the EGR will open up and send the burnt exhaust gases back into the combustion chamber cooling the combustion temps and lowering the NOX levels.
The EGR valve might test good but, it's just not opening up at the correct time.
Re-install the stock exhaust components and with the added back pressure the EGR will open up and send the burnt exhaust gases back into the combustion chamber cooling the combustion temps and lowering the NOX levels.
The EGR valve might test good but, it's just not opening up at the correct time.
Last edited by GKK; Mar 19, 2010 at 02:52 AM.
Instructor
Joined: Feb 2009
Posts: 145
Likes: 0
From: Colgate WI
But a brand new 3-way cat on the car, drive it for 100 miles then take it in for the test. I can almost guarantee you will pass.
The only thing that controlls NOx on a car is the EGR and the CAT. Even if they say the cat is working, a new one will cover up a LOT of emissions problems and get you through a test. Make sure you drive it 100 miles to burn out the manufacturing oil tho!
The only thing that controlls NOx on a car is the EGR and the CAT. Even if they say the cat is working, a new one will cover up a LOT of emissions problems and get you through a test. Make sure you drive it 100 miles to burn out the manufacturing oil tho!
Thread Starter
Advanced
Joined: Mar 2010
Posts: 72
Likes: 1
From: Phoenix AZ
Thanks for the suggestions all. Turns out the cats were in fact bad. New cats and a tune to fix a lean condition at cruise and tip in and the car passed with flying colors! Runs so much smoother now as well.
Safety Car
Joined: Aug 2008
Posts: 4,344
Likes: 48
From: San Marcos CA
The free flowing exhaust (headers, cat & x-pipe) are contributing to a Lack of Exhaust Back Pressure which the EGR valve needs to operate correctly.
Re-install the stock exhaust components and with the added back pressure the EGR will open up and send the burnt exhaust gases back into the combustion chamber cooling the combustion temps and lowering the NOX levels.
The EGR valve might test good but, it's just not opening up at the correct time.
Re-install the stock exhaust components and with the added back pressure the EGR will open up and send the burnt exhaust gases back into the combustion chamber cooling the combustion temps and lowering the NOX levels.
The EGR valve might test good but, it's just not opening up at the correct time.
btw, a bigger than stock cam with a little overlap will reduce combustion temps and help lower nox at low engine speeds/loads. what might be getting you are those cheap *** catalysts that might not be very good 3-way converters. the oem drum units will clean the exhaust to nothing- they are really high capacity scrubbers.
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