Emission test.

gmctrucks · 01-16-2009, 08:07 PM

Emissions test-OK here in Houston we have to pass that smog test now I have a 1993 F/S GMC with a 5.7 engine now each year that I go and get it tested I barley pass could it be that im running regular unleaded gas instead of using super unleaded my chip calls for? What the tech always says is that my Cat is bad but I have a new cat or he said that it could be my EGR valve what do you guys think sorry for the grammar.
Thanks! GMC

PS-Should I fill it up with super unleaded and drive my truck around or warm the engine up before I take it how about one of those cans of pass emissions test guaranteed? I'm taking it tomorrow so help.

mudseeker · 01-16-2009, 08:11 PM

nothing you can really do if the test is tomorrow...............

bradrhale · 01-16-2009, 08:16 PM

without knowing the numbers, its hard to tell. they test for more than Co and Nox. find out what number you are reaching the limits on, and we might be able to narrow down what your problem might be.

gmctrucks · 01-16-2009, 08:34 PM

Well I don't have to get it done tomorrow I have till the end of the month so im going to look for the test results tomorrow im thinking that it was high on Nox.

mudseeker · 01-16-2009, 08:36 PM

nox could be a faulty EGR. i hate OBD1, the sensors seem stoneage compared to what i'm used to working with.

Kennyray · 01-17-2009, 04:37 AM

On other sites I have browsed they recommened an oil change and fresh tune up right before getting tested.

leolkfrm · 01-17-2009, 05:08 AM

Um chip! more fuel more power. pull the chip and drive it a couple of days before the test. plugs under 10,000miles, some injector cleaner in the tank the week before before the test, then fresh fuel.
a scanner may show something, as far as readings. I would also consider blowing the snot out of it the day before the test
Just some thoughts, I glad we don't have the sniffer test

stumpuller454 · 01-17-2009, 07:40 AM

NOx is created under high cylinder temps, there are many ways to lower it, increase timing, use better fuel, cooler engine (thermostat working good?) cooler intake air, less exhaust restriction, richer mixture (although this usually affects other hydrocarbon levels.)

gmctrucks · 01-17-2009, 09:00 AM

I was thinking of removing my chip and cleaning my K&N air cleaner and I know that a set of plugs would help since I have tons of miles on them. Now I checked the EGR it's working good but I guess a can of Seafoam wouldn't hurt im going to do the Seafoam dealy using my brake vacuum line. Now Stump what do you think about me leaving the chip and go with super unleaded like it ask for or should I add super unleaded and remove the chip im so confused? Hey guys thanks for all the feed-back you guys are the greatest.

gmctrucks · 02-03-2009, 04:49 PM

UPDATE----OK members I took my truck in today to get my inspection sticker but before I Seafoamed it and I replaced my air filter since my K&N needs to be serviced and I was lazy to do it then I drove it around 45 miles to get the Cat nice and hot then I took it in and it PASSED well the only thing that failed was the locking gas cap so I bought one there so now im ready to drive around the world. Now what I noticed is the tech keep the rpm's low while doing the test I think that might have helped it and it's wasn't that hot today I was kinda worried there because it was taking a while to complete the test but it passed.
He! He! GMC
PS-I also had my buddy run his Snap-On scanner on it before I took it and it was coming up with EGR which would give it high readings on NOX so he cleared it but on my way the get the sticker the check engine light came on so I pulled over and turned off my truck and the light turned off but again it passed which im a happy camper. I really thought it was going to fail because of a bad EGR valve.

01-16-2009, 08:07 PM	#1
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 4,645	Emission test. Emissions test-OK here in Houston we have to pass that smog test now I have a 1993 F/S GMC with a 5.7 engine now each year that I go and get it tested I barley pass could it be that im running regular unleaded gas instead of using super unleaded my chip calls for? What the tech always says is that my Cat is bad but I have a new cat or he said that it could be my EGR valve what do you guys think sorry for the grammar. Thanks! GMC PS-Should I fill it up with super unleaded and drive my truck around or warm the engine up before I take it how about one of those cans of pass emissions test guaranteed? I'm taking it tomorrow so help.

01-17-2009, 05:08 AM	#7
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 4,932	Um chip! more fuel more power. pull the chip and drive it a couple of days before the test. plugs under 10,000miles, some injector cleaner in the tank the week before before the test, then fresh fuel. a scanner may show something, as far as readings. I would also consider blowing the snot out of it the day before the test Just some thoughts, I glad we don't have the sniffer test __________________ 4 wheels move the body 2 wheels move the soul B.W.A.I

01-17-2009, 07:40 AM	#8
stumpuller454 Senior Member Join Date: Dec 2007 Location: Grande Prairie, AB Posts: 2,206	NOx is created under high cylinder temps, there are many ways to lower it, increase timing, use better fuel, cooler engine (thermostat working good?) cooler intake air, less exhaust restriction, richer mixture (although this usually affects other hydrocarbon levels.) __________________ SUPERCHARGED 454 K2500 GMC! Watch My Youtube Videos!!<<<

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01-16-2009, 08:11 PM	#2
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 7,155	nothing you can really do if the test is tomorrow...............

01-16-2009, 08:16 PM	#3
bradrhale Senior Moderator Join Date: Apr 2006 Location: Texas Posts: 9,558	without knowing the numbers, its hard to tell. they test for more than Co and Nox. find out what number you are reaching the limits on, and we might be able to narrow down what your problem might be.

01-16-2009, 08:34 PM	#4
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 4,645	Well I don't have to get it done tomorrow I have till the end of the month so im going to look for the test results tomorrow im thinking that it was high on Nox.

01-16-2009, 08:36 PM	#5
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 7,155	nox could be a faulty EGR. i hate OBD1, the sensors seem stoneage compared to what i'm used to working with.

01-17-2009, 04:37 AM	#6
Kennyray Senior Member Join Date: Oct 2005 Location: Birmingham, AL Posts: 895	On other sites I have browsed they recommened an oil change and fresh tune up right before getting tested.

01-17-2009, 09:00 AM	#9
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 4,645	I was thinking of removing my chip and cleaning my K&N air cleaner and I know that a set of plugs would help since I have tons of miles on them. Now I checked the EGR it's working good but I guess a can of Seafoam wouldn't hurt im going to do the Seafoam dealy using my brake vacuum line. Now Stump what do you think about me leaving the chip and go with super unleaded like it ask for or should I add super unleaded and remove the chip im so confused? Hey guys thanks for all the feed-back you guys are the greatest.

02-03-2009, 04:49 PM	#10
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 4,645	UPDATE----OK members I took my truck in today to get my inspection sticker but before I Seafoamed it and I replaced my air filter since my K&N needs to be serviced and I was lazy to do it then I drove it around 45 miles to get the Cat nice and hot then I took it in and it PASSED well the only thing that failed was the locking gas cap so I bought one there so now im ready to drive around the world. Now what I noticed is the tech keep the rpm's low while doing the test I think that might have helped it and it's wasn't that hot today I was kinda worried there because it was taking a while to complete the test but it passed. He! He! GMC PS-I also had my buddy run his Snap-On scanner on it before I took it and it was coming up with EGR which would give it high readings on NOX so he cleared it but on my way the get the sticker the check engine light came on so I pulled over and turned off my truck and the light turned off but again it passed which im a happy camper. I really thought it was going to fail because of a bad EGR valve.