5sfe failed on NOx emissions

[dammule]

Here is some history before I ask a question.

About a 1.5 years ago, We (my father and I) replaced my timing belt, water pump, a pulley, and some necessary seals. When we put the car back together, it idled much faster than originally. normal is 850-950 +- mine idles around 1200rpm. After we went through forums and asked a few mechanics, and literally spent 3 weekends troubleshooting different things, it became apparent that the timing gear was off by a tooth. This we know!
This is not my question.

Shortly thereafter, My car failed emissions. Again, this was last year. NOx allowable is 984 and mine had around 1080 ppm A mechanic told me to replace the EGR solenoid and I did, It barely passed.

This year it failed much worse, but still on NOx. I had a feeling that maybe it was something else but tried a new EGR first. (40 bux)

People have told me the catalytic converter on these cars pretty much never goes bad. Also, if I did want to replace it (if it is the problem) it would cost around 500.00 because of the unique design, location of the cat.

HERE IS MY Question !!!!!!
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IF I simply retard my timing, Does anyone know if it will make enough difference to lower my NOx emissions to a passing level. The current reading is 1279 allowable is 984. Or Do I need a cat?

Thanks a bunch!
Dammule

[TomsMR2]

People have told me the catalytic converter on these cars pretty much never goes bad.

people are wrong. its pretty common for them to go out.. especially considering how rich our engines burn, and how extremely common oil burning is.

install a SECOND cat, behind the xmember on the b-pipe. use a cheap 50$ obd2 cat. you could even cut a section out with a hacksaw, and clamp a new cat in place.. in general its cheaper to just toss a cat at the car than to continue failing, replacing parts, and retesting.

[Enthalpy]

High NOx is caused by bad cat, lean mixtures or overly-advanced timing. If you changed your timing belt, make sure the CAM timing is spot on as well.

Retarding the timing does reduce NOx quite a bit, yes. If the timing is overly advaned, then that's your problem. If not, then that's only a band aid. You need to figure out why it's doing this. You might be running lean because of clogged fuel injectors, which is very common on older cars. Your O2 sensor might need help.

[TomsMR2]

overly retarded will do it too. anything raising EGT's will.. normal, standard operation raises EGT's high enough to create NOx as-is... in the grand scheme of things, your car is at least 12 years old and probably has 100K+ miles on it, the cats just worn and tired at that point, emissions is always going to be a struggle with the primary component that old/worn.

with a good cat, you could pass smog at 15 degrees btdc while running lean with a slow o2 sensor. a good obd2 cat in the b-pipe is pretty close to a sure-fire guaranteed pass.

[Enthalpy]

Lean mixtures raise EGT, but also create NOx. EGT is not a conclusive indication of NOx content.

It's true, your cat could be damaged from misfires, oil or coolant in the exhaust, overly rich mixtures for long periods of time, etc.

[Ben]

NOx Is Mostly EGR As You Know. You Said You Replaced Your EGR, But For $40. Did You Just Replace The EGR Modulator? I Would Also Clean Out The EGR Hard Pipe That Goes From The Cylinder Head To The EGR - This Gets Plugged With Carbon Build Up And Increases NOx.

Test The EGR VSV And Be Sure That It Is Still Good, If It Is Not Switching Correctly The EGR Doesn't Work Properly.
Check Your Vacuum Lines, I Was High On NOx And Found A Bad Vacuum Line That Went To The Throttle Body.

Don't Retard The Timing Too Much. You Can Fail Just For Having Incorrect Timing.

[mr2greasemonkey]

if your egr is functioning correctly you should be able to stall the engine at idle by applying vacuum to the valve.

[TomsMR2]

EGT is not a conclusive indication of NOx content.

NOx forms at a certain temp, and only past that certain temp. its directly related to temperature. you cant quantitively measure it by temp alone, but it only starts to form when the temp is right.. if the temp is up, and combustion is happening, its breaking down into nox, it'll just do it more or less if its rich or lean.

edit: more specifically, cylinder temps.. egt usually isnt measured until its out of the port.. by that time it cools too much.. the nox is formed in the cylinders, not really out the ex ports. egt was kind of inaccurate : /

[dammule]

Originally Posted by TomsMR2

people are wrong. its pretty common for them to go out.. especially considering how rich our engines burn, and how extremely common oil burning is.

install a SECOND cat, behind the xmember on the b-pipe. use a cheap 50$ obd2 cat. you could even cut a section out with a hacksaw, and clamp a new cat in place.. in general its cheaper to just toss a cat at the car than to continue failing, replacing parts, and retesting.

[dammule]

-This car is a non-turbo. I have no B pipe. Thanks though.

-The Egr test works out fine. If I hold it closed it stalls. Thanks

I know for a fact the timing is off a tooth. When we took it apart we marked it with paint pen, and when we put it back together, we put it on the wrong side of the paint. We didn't realize it until it was all back together. I have gone to 4 muffler shops and they all told me the cat just about never goes bad. We had it off and it looks very clean inside.

So right now it could be a number of things.
1. a turbo with a b-pipe (which it's not)
2. a problem with my timing. I'm pretty sure thats the one
3. a problem with my egr. But it tests okay and the hard pipe is good.
4. my cat. Which 4 supposed experts say is not it.
5. My o2 sensor. Hmmm here's one I haven't looked into. I will check into it

more history.
Car has 209,000 + miles on it. Runs fine. other than fast idle and the NOx failure. Always use Mobil 1, changed sparkplugs, plat +4, Nology wires
HKS intake, New alternator, New valve cover gasket, new cap+rotor, new EGR VSV.... any more ideas?

[Mister2.2]

Turbos have down pipes, non turbos have B pipes, you have a b pipe.

[PearlJammzz]

Try sensor and timing and let us know. It may be a slight combo of both.

[dammule]

okay thanks. Preciate all you guys!

[dammule]

oh and 1 more thing... Anyone priced one of these factory cats? Just curious.

[Enthalpy]

Originally Posted by TomsMR2

NOx forms at a certain temp, and only past that certain temp. its directly related to temperature. you cant quantitively measure it by temp alone, but it only starts to form when the temp is right.. if the temp is up, and combustion is happening, its breaking down into nox, it'll just do it more or less if its rich or lean.

edit: more specifically, cylinder temps.. egt usually isnt measured until its out of the port.. by that time it cools too much.. the nox is formed in the cylinders, not really out the ex ports. egt was kind of inaccurate : /

What about detonation? This is a circumstance where all of your requirements are met, yet EGT is WAY down and NOx is WAY up.

Just read your edit. Yes, CYLINDER temps are a direct indication of NOx. EGT is not.

Sorry about that.