ittybittyfds

i failed my emissions today

they call it a NOx failure....
Oxides of Nitrogen....

any input would be nice

C4Techie

EGR valve.

rickneworleansla

I believe the EGR system is responsible for NOx.

ittybittyfds

my state standards are 2.8000 GPM
my readings were 3.1998 GPM so i am high
is there a way to test the EGR or is it easy enough to just replace

jaa1992

Find the EGR valve and apply vaccum to it - do you hear the valve move? Does it hold vaccum?
If the valve doesnt move or it doesn't hold vaccum replace it - if it does both remove and clean it, replace the EGR selenoid. Don't know where it is on the 85.

Just had to replace both the valve and selenoid on my 92.

flatbush862

I had a high NOx reading during an inspection on my '90. I was told because of a hugh carbon buildup in the head, too much heat was being generated during combustion. The shop perfomed something called an "engine vac." where the carbon is cleaned out internally. I think it was about $130. I don't know how this compares with the cost of another EGR, but it definitely worked. Although the CO was bumped up slightly, the NOx came way down

flatbush862

I had a high NOx reading during an inspection on my '90. I was told because of a hugh carbon buildup in the head, too much heat was being generated during combustion. The shop perfomed something called an "engine vac." where the carbon is cleaned out internally. I think it was about $130. I don't know how this compares with the cost of another EGR, but it definitely worked. Although the CO was bumped up slightly, the NOx came way down

Bad Karma

The best part of this is that the EGR is also the reason the carbon built up... since you are pumping dirty exhaust gas into the engine.

With the EGR system working properly, it will lower your NOx emission, but at the cost of raising your *** emissions.

SunCr

Interesting, but I would be more inclined to believe that it's burning oil, particularly if the mileage is up there. Of course that would, over time, diminish the effectiveness of the CAT, leading to higher emissions. If it were mine, I'd check compression or do a leakdown test or maybe just hook up a vacuum gage.

ittybittyfds

so SunCR im gonna ask a potentially stupid question.
"how do you tell if your burning oil?"
i have considered this but since she only has 70,000 miles on it and it has always had the regular maintenance done always. i dont want to fathem that its burning oil however there have been a couple of time recently when i can smell it. I also check for any oil leaks after i sits all the time.
i have also noticed that my oild pressure is higher now then normal

i am now usually between 69-72 were it normally was always around 60

SunCr

That's low mileage for an oil burner. The LT motors - at least according to one of the mags - have an appetite for valve seals - which if worn, would allow oil into the combustion chamber. But, you didn't post your Year. If it's using more than a quart every 3,000 miles, I'd dig into it or since you're smelling something, I'd start by hooking up a vacuum gage and see what's it's pulling and verify that the needle is steady - somewhere around 16 to 18 at idle. You could also remove a plug or two and see what they look like. If you have a scanner, you might check fuel delivery too - could be a rich condition.

Perfusion

I failed CA SMOG last summer on NOx. Believe it or not, a can of SeaFoam worked wonders - it cut my level in half, actually slightly more than half.

For $8.99, it's a helluva cheap thing to try first before you dig into expensive repairs.

C4Techie

That would take the place of a $130.00 "engine vac".The "engine vac" addresses the problem from a different cause than the EGR valve. Verify the operation of the valve as outlined in the earlier thread.

ittybittyfds

oki will look at the haynes manual and start looking at vacume pressure and plugs as well....
Sorry...it a 85 L98 4+3
what the hek is seafoam

i want to do that anyways because of some idle issues i have even after changing the TPS

Perfusion

http://www.seafoamsales.com/motorTuneUp.htm

If you're skeptical, as you should be by a complete stranger telling you to pour an unknown product into your car, just do a forum search. I think you'll find enough positive opinions for peace of mind.

SunCr

But then if you put "Sea Foam Problems" in Google you'll find other opinions and a few ruined engines. I'm not saying not to use it - but why not find out why there's so much carbon on a low mileage motor first - particularly one that's designed to run on a fairly clean mix?

JrRifleCoach

Whats your base timing set at?

For testing purposes, try retarding by 2-4 deg. It does work!

tdr1919

I am also failing on NOx and HC's & CO my 86 base timing id 6 deg. if I go to 8 or 10 deg. will that help with the emissions?

Thanks,
Tom

SunCr

To fail on everything points to a dead cat (or maybe a non functioning air pump) but to be sure, scan it and make sure fuel delivery is correct. You will spend far less money doing that than throwing parts at it in hope of a quick fix.

I don't go along with retarding timing to resolve a lean condition. If combustion temps are high enough to cause excessive NOX, it's probably detonating too, which (to me) means it's less than it can/should be as the Knock Sensor (you hope it's working) is reducing performance. If your Vette is a stock DD, these emissions tests should be your friend. How many cheap opportunities do you get (well it costs about 50 Bucks out here) to have a probe stuck up the tailpipe to show you what the quality of the combustion process is?

GKK

I read in your profile that you have Longtube Headers and a high flow Cat installed. The EGR needs a certain amount of exhaust backpressure to operate correctly which injects some exhaust gas into the combustion chamber which cools the combustion chamber and reduces the NOX readings.

I once had a "91" stock Camaro RS with a Random Tech Cat, SLP Y-Pipe and Flowmaster exhaust. I failed California emissions 3 times until my mechanic finally convinced me to replace with a stock Cat and remove the high flow Y-Pipe. He said the EGR didn't have enough backpressure to operate correctly.

The Camaro finally passed. Some members who have installed Headers and high flow Cats, pass emissions easily and some don't.