Come to think about it, my cats had failed also, so that test includes 2 new cats...

try with the O2's first, you will probably pass.

 

The O2 sims are just for the rear, but they won't make you pass if your cats are failing.

 

This puts you at a disadvantage with regard to NOX. That's the reason the car is designed to run a little hot. You loose power/performance but gain emissions/performance. With one strike against you, the NOX issue will magnify as your other sensors age and under perform. If you go back to hot, you might be OK, even though other emissions sensors are starting to age and get sluggish.

no - this simulates wind going over the car while you are driving

 

Try the drygas trick.

 

i think im going to put back the stock thermostat and new front 02's for the test. Will the stock tstat help me run warmer?

And i was under the impression that the dry-gas worked if you were failing in other areas, but would increase combustion chamber temps and increase NOx.

 

Yea, the stock t-stat will warm things up. The EGR works by injecting hot exhaust in to the cylinders, which raises combustion temperatures and reduces NOX. The stock t-stat will warm the sides of the cylinders, which will also raise the combustion temperatures in the cylinder by a little bit.

Not familiar with dry gas, but if it increases temperatures in the cylinders, that should also help.

New O2s are always a good thing. If they are old, they could be leaning out the ratios and leading to more NOX.

 

thanks i have some denso o2 sensors on order. And my stock tstat is still in my room somewhere.

Also for the dry gas people are using this stuff called "iso-heet" they pour a few bottles (12oz each) into a 1/4 tank of gas. I have to check and see if autozone carries it.

 

no, the egr works by injecting exhaust gas into the cylinders which lowers combustion temps, because the exhaust gas which does not burn dilutes the air/fuel mixture.

NOx is created by high combustion temperatures. To reduce NOx, you need to lower combustion temperatures.

 

So sorry, this is correct. I must have been having a massive brain fart and was confusing HC with NOX. I'll do my homework next time: http://www.autoshop101.com/forms/h55.pdf

If the EGR is good, then it must be an air/fuel mixture issue. (I suspect if the CAT was bad, you'd have NOX in all conditions.) O2 sensors are the best thing to change, then - or you may even want to replace the fuel filter if you haven't done that in a while.

 

first, a new air filter or fuel filter won't affect ****. you're wasting your money on stuff like that. If the fuel filter were clogged, that would show up as loss of power and sputtering under throttle, but it would never affect emissions. Fuel filters rarely ever clog. And the air filter won't help anything, the amount of air entering the engine is measured by the MAF meter, and that is behind the throttle plate which is what restricts the amount of air entering the motor to control it's rpm. So an air filter clogged is no different than the throttle plate closed which lets the engine idle. you could block off 3/4 of your air filter with cardboard, it would have no affect on emissions because any and all air entering the engine is measured by the maf and in closed loop mode the front O2's verify proper air/fuel mixture.

You did not clarify what the test encompasses, do they also do an idle test not in gear? how about under a load with decent throttle?
you also did not mention whether you have an auto or manual trans, and how did they run the car for the 15 mph test? If it were an O2 sensor I would think you would be off at all rpms and loads, since you are buying new ones i hope they help. Dry-gas or iso-heet is just isopropyl alcohol and/or methanol. When added to gasoline it helps water mix in and disperse and will allow water to pass through the motor and not affect combustion like straight water in gasoline which does not mix. But what alcohol/methanol also does is lower combustion temps, think of top fuel alchohol dragsters except you're not passing over a gallon/sec through the engine like they do. add 2 or 3 bottles to like 1/2 tank, that will kill overall performance and engine power, not enough for daily driving, but definitely helps with nox emissions. what you can also try, is find the relay to the air pump and jump it so the air pump is running, that'll inject fresh air into the exhaust manifold diluting the exhaust gases and lowering all the numbers, and possibly helping with catalytic converter efficiency. This will all help with a stock setup, if you have a different cam or had a tune then all bets are off.

 

As an ex certified emissions inspector in Ohio I can tell you for NOX you need to focus on the E.G.R system or the Cats.. Those are what will affect NOX. If your cats are marginal you want to get them as hot as possible. Don't just drive it around, whip the dogshit out of it before testing. Don't shut the car off before testing and risk being in open loop. If your E.G.R. system is O.K. it's probably going to have to have cats.. It's not possibly knocking at the range where you fail is it?

 

If the O2 sensors are old, wouldn't that cause them to under estimate the amount of air in the mix, lean out the air/fuel mixture, and cause a greater potential for NOX?

 

the car is an m6 pretty much stock

the test on the rollers is done at 15mph and 25mph in second gear and they stick a meter in the tail pipe. I am only having trouble with the 15 mph test. There is no idle test.

before my next test i will be changing from a 160 tstat to stock, installing new o2s, and adding iso-heet.

Jumping the air pump relay sounds like a good idea, but im not exacly sure how to do that. Is the only thing you need a spare wire?

 

From experience doing repairs to pass the NOX portion, no.
Theoretically possible, sure. It would generally have insufficient switching codes 171,174 (lean), even then I have never seen an o2 be the cause. My money is on the cats., they probably work well enough to not trip efficiency codes but can't handle the NOX. There was a time in Ohio where a brand new cat. would fail NOX unless it was OEM. The aftermarket ones would fail brand new.

 

Do you have a skip shift eliminator on the car? I wonder if having the car force them in to 4th gear would change things?

 

that's what i was thinking of if he had a manual, which he does. emissions has been shutdown twice in my state for them being crooks and idiots, they once tried to sniff the tailpipe on my diesel truck until their boss told them it was a diesel. they are state workers so don't expect them to know or care, they would have no idea that they are in 4th gear and if the engine is lugged at 15 mph it would produce more nox. at 25mph the rpms are high enough to where the engine isn't lugging and that's why it's passing at 25 but not at 15mph. they probably assume 2nd gear because any auto trans would be in 2nd gear at those speeds.

 

for 15mph he was at 1300rpm
for 25mph at 2112

i think those match up with 2nd gear pretty well. but i was thinking the same thing.

 

I used to have this issue every time in NY until they switched to PCM monitoring only.

In addition to dry gas, I have used 4 to 5 onces of acetone in the gas per 1/2 tank.

This does not harm any parts and it works!

 

Unless you have to pay everytime for a retest, if I were you, I would seriously just try the iso-heet. Get 3 or 4 bottles and throw it in a half tank or even less. Drive the dog **** out of it, and take it up to get tested and if you can, like has been said, leave it running. I would almost bet you will pass with flying colors. But I totally understand if you have to repay every time for a retest. Just trying to save you time and money and aggrevation. I've just seen how well that dry gas trick works personally and it's amazing. The other poster above gave the perfect description of what happens pretty much.

 

thanks for your input, since i already paid for the o2s im just gonna wait till they get here and install them, but i will be trying the iso-heet trick for sure. its sold at standard auto parts stores, correct?