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cutsupreme 10-09-2003 08:52 PM

Emissions HELP
 
I have an 85 cutlass supreme. This means I still have to pass the emissions test.

So of course I go to get my car inspected, safety passes fine but I fail emissions.
Does anyone know an easy way to lower the emission the car produces.
I went to a shop and the guy said it could be the timing chain, and that would be pretty expensive to fix.
Does anyone have any other ideas that can help me pass emissions.

Thanks for any input

Jmark 10-09-2003 08:58 PM

It all depends on where it failed. HC? CO? at idle? or at cruise? Post some numbers and we'll do our best. ( I doubt the timing chain caused the failure!)

Mark

TooMany2count 10-09-2003 10:03 PM

try these 3 things just before you get it tested,
1st always change the oil before you get a car tested, because it will have a certain amount of gas contamination in it and will cause your cars to fail at times.
2nd either change the air filter or take it out (just for the test) that way it sucking in cleaner air.
3rd. this is a cheater but remove the PCV and just lay it on the valve cover BUT still attached to the vacuum line, this also will let your car suck in cleaner air.
i did these thing on my 84 burb because it had failed BADLY, & by doing these thing it passed w/flying colors..........joe

scholman 10-09-2003 11:15 PM

Cutsupreme,

As long as you do not have any internal problems like burn valves or bad rings, try pouring in a bottle of "Guaranteed To Pass".
I put it in my 76 Sprint and followed the directions to the letter and I passed with now worries. They say on the bottle that if you do not pass they will pay for your testing. Check it out.
I would not try to cheat the system because if you get caught you may have to go to a "Check Only" station everytime from then on. I don't think it is worth the headache.
Also set the timing to factory specs, even if the car runs like trash. The machines that test go by factory settings so stick to them until you get your OK from the state.

Keep it clean
Scholman

cutsupreme 10-10-2003 02:45 PM

Thanks for the input so far

Here are some numbers for what I failed

CO GPM 058.08 it says the limit should be 030.00
NOX GPM 03.48 limit on this 03.00

Hope this will help
thanks

Jmark 10-10-2003 03:21 PM

Well, its running too rich, ( high CO) and I'd take a guess that the EGR valve is not working properly ( high NOX)
What was the HC reading?

cutsupreme 10-10-2003 04:04 PM

HC is 01.74

That one passed

Jmark 10-10-2003 04:15 PM

You could try leaning the idle mix a little and make sure the air cleaner and pcv valve is good.

Grams Per Mile testing takes into consideration all aspects of driving, idle, accel, cruise and de-cell. Kinda hard to trouble shoot without idle and cruise readings.
Here in AZ, we have idle and cruise only, no "GPM". Makes pinpointing the problem a little easier.

As far as the NOX goes, you need to ck your EGR valve. You can get a piece of vac hose and hook it to the egr and start it up and suck on the hose. If it is working, it should open and the idle will go to crap and probably die. Some engines require some amount of exhaust backpressure before the egr will open though, not sure on yours.

If the EGR works ok, ck the timing, idle speed, plugs and wires, if all are ok, give it another try, it might pass this time.

cutsupreme 10-11-2003 08:33 AM

Where is my egr valve located
3.8L v6

dmorris1200 10-11-2003 10:31 AM

A NOX failure is often caused by a faulty EGR (not opening or clogged passage) but because of the opposite reason Jmark gave. NOX failures mean that the combustion temps are too high. This is caused by lean mixtures. You have provided almost no worthwhile info to help you out (base timing, vacuum advance hook-up, etc.) A lot of the routine suggestions may help. Leave your PCV hooked up but pull it out of the valve cover so it's sucking in fresh air. Get your base timing set correctly, as mentioned retarding the timing kills performance but often helps pass emissions testing. If your vacuum advance is connected to manifold vacuum switch it to ported, this will allow your timing to stay at base timing when idling. After making all adjustments last but not least set your idle on the high side, not high enough to fail for excessive rpms but just below the max allowed. As far as properly tuning your carb, that I will not get into over the internet. Another major factor you have not mentioned is whether or not your car is fuel injected or carbed. Either way if it is a computer controlled carb with a M/C solenoid or fuel injected just changing the O2 sensor could get you a passing test.


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Jmark 10-11-2003 10:48 AM

Quote:

Originally posted by dmorris1200
A NOX failure is often caused by a faulty EGR (not opening or clogged passage) but because of the opposite reason Jmark gave. (HuH?)
NOX failures mean that the combustion temps are too high. This is caused by lean mixtures.


Don't know where the confusion came from in my previous post, but I"ll re-write my first sentence.

"As far as the "high CO failure" goes, You could try leaning the idle mix a little and make sure the air cleaner and pcv valve are good.

Seems to me that if he is failing because of "high CO", its not lean. An in-operative EGR will cause combustion temps to rise ( because the engines are designed to run super lean anyway) and increase NOX readings. The main purpose of the EGR is to cool the combustion temps to keep NOX down.

As far as leaving the pcv laying on the valve cover sucking fresh air, thats an automatic failure here is AZ, no questions asked, your done, see ya tomorrow.

Leave out the air cleaner, same thing.
Un-hook the advance, same thing.

dmorris1200 10-11-2003 11:03 AM

Actually if you think about it, the EGR's job is to richen the mixture. That's why when it isn't working the engine runs too lean, usually pings, and fails for NOX due to increased cumbustion temps. What's interesting about his failure is that a failed CO could often mean different things in different applications. Any poor combustion could raise CO's (incomplete burn of fuel mixture) but his high NOX also tells a story of a lean mixture causing high combustion temps. Were his readings at idle, at elevated rpms? High combustion temps caused by excessively lean mixtures due to a faulty EGR could also cause poor combustion events causing CO's to increase. There are a lot of variables to this kind of stuff, it's not always as simple as 2+2=4. I agreed with the possibility of a faulty EGR as a possible cause but not because it causes a rich condtion. Rich conditions lower NOX readings.

PS. I don't think anyone said to un-hook vacuum advance, and yes if he is in a state that requires openning the hood like during an IM240 test he must leave pcv in the valve cover.

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Jmark 10-11-2003 05:27 PM

Im' sorry Dmorris, but I will have to completely dissagree with almost everything you have stated.

Quote:

Originally posted by dmorris1200
Actually if you think about it, the EGR's job is to richen the mixture. [/i]
The EGR valve will not richen up the mixture. Its only function is to open when necessary, either by a vacuum signal, or electronically and recirculate exhaust gas back into the air/fuel stream to cool down the combustion temperature, which in turn will help reduce pinging, therefore resulting in a lowering of the NOX emissions. It cannot richen up the mixture. Its introducing an already burned mixture back into the engine. Its basically a neutral gas, it contains virtually no usuable oxygen or fuel.
That is why the EGR is NOT designed to work at idle and low throttle openings.
If you've ever opened an EGR valve manually at idle, what happend? The engine leans out, stumbles and usually dies if you continue to keep the valve open. Why? Because it does not contain enough oxygen or fuel to aid in further combustion.
If, in fact, it DID richen up the mixture, it would run better at idle with the valve opened and would have no negative affect at idle and low throttle openings.

Quote:


That's why when it isn't working the engine runs too lean, usually pings, and fails for NOX due to increased cumbustion temps.



Sorry, but when the EGR valve fails to open, the resulting mixture is NOT diluted with exhaust gas and and will actually be marginally richer. More importantly however, the temps in the combustion chamber will still be too high, pinging may accure and NOX polutents will be high, as the engine is designed to, and will be running on the lean side anyway.
In my previous posts, I never said that a bad EGR will cause a high CO failure. I said the engine was running too rich, fuel problem,( high CO failure) and that there was most likely an EGR failure too, ( high NOX reading) Two different problems, two different emission readings and two different "fixes".

Quote:


What's interesting about his failure is that a failed CO could often mean different things in different applications. Any poor combustion could raise CO's (incomplete burn of fuel mixture) but his high NOX also tells a story of a lean mixture causing high combustion temps.



First off, CO is burned gasoline.
High CO is NOT caused by incomplete combustion. If you have low CO readings, all it means is you have successfully burned all the fuel in the combustion process. Low CO readings are a good indicator of a properly set carb or injector system, showing that all the fuel has been properly burned and that the engine is not over rich.
If you have high CO readings, all that means is you have successfully burned a very rich mixture.

Second, HC ( hydrocarbons) is nothing more than raw, unburned gasoline.
Poor combustion will not raise the CO level. If you have poor combustion, as in incomplete combustion, the HC readings will be high, because you are not completely burning all the fuel, giving you raw fuel leaving the cylinder and exiting the vehicle. If the fuel is not being burned, it cannot turn into carbon monoxide, (burned fuel)
His HC readings were fine, showing that he basically had good combustion, just too much fuel in the mixture.



Quote:


Were his readings at idle, at elevated rpms?



No one knows for sure. The "Grams Per Mile" test does not break it down into seperate readings. But by his readings, we do know that one:
there is too much fuel being introduced into the engine at some point, causing a high CO reading.
and two:
That it is very probable that the EGR valve is NOT doing its job, for whatever reason, resulting in higher than normal combustion temps, probable pinging and giving a high NOX reading.


Quote:


High combustion temps caused by excessively lean mixtures due to a faulty EGR could also cause poor combustion events causing CO's to increase.



Again, a non-functioning EGR valve will not result in a lean mixture. It will, however, result in higher than desired chamber temps, which will increase the chance of pinging and elevated NOX readings.
Again, poor combustion will not raise the CO levels, it will raise the HC levels. ( poor combustion is the incomplete burning of the mixture, resulting in un-burned fuel, "hydrocarbons", leaving the exhaust system and giving a high HC reading.)

Quote:


There are a lot of variables to this kind of stuff, it's not always as simple as 2+2=4.



Yes, there are alot of variables in this, but without knowing where the rich mixture is comming from, ( idle or cruise), its very hard to give the proper advice.
My suggestion to try to lean out the idle mix was given because that is the simplest and easyest way to affect a change in CO without going into the carb, if so equip't.

Quote:


I agreed with the possibility of a faulty EGR as a possible cause but not because it causes a rich condtion. Rich conditions lower NOX readings



Again, I never stated that a faulty EGR will cause a high CO failure. I stated that he had 2 different problems, both resulting in the vehicle failing the test.

While its possible that a richer than normal mixture may result in a slightly cooler combustion chamber and lower NOX readings, at that point you would have too high of a CO reading, failing the test again.
Maintaining proper emissions is a balancing act between having just barely enough fuel in the engine to have COMPLETE combustion,(acceptable CO and HC readings.) but fighting high chamber temps and pinging at the same time.


My suggestion is to take your car to a shop that has a 2 gas analyzer and watch the CO reading as you open the EGR valve at idle. As soon as its opened, the CO will go down and the HC will go up. The mix is leaned/diluted and the amount of burned fuel goes down, ( low CO) and at the same time, the mix is too lean/diluted to COMPLETELY burn, giving you high HC readings, (raw un-burned fuel)

Mark

tm454 10-11-2003 06:04 PM

I hate these emissions systems on the newer cars
 
My newest ride is a 74 Dodge PU truck. I really love NOT having to get tested every other year. Sorry to hear about your problems, don't forget to get the timing chain repair done as soon as possable.



Todd



Rat Rods Rule!

dmorris1200 10-11-2003 08:01 PM

Well I guess some of this will forever be interpretational. EGR gasses lower the total volume of combustable gasses in the cylinders. I guess I interpret the fact that these gasses reduce the amount of clean air(combustable oxygen) that can enter the combustion chamber that it is almost the same as richening the combustion mixture since the inert exhaust gasses are lacking in burnable oxygen. That may not be the most acurate analogy. And EGR's are designed to allow an exact amount of flow as well, to much is as bad as too little. I could dump raw fuel down a carb at idle to and it would stall, not because its too lean. I would also like to quote this from a manual..."Carbon monoxide (CO), is incompletely burned fuel or to be more precise are hydrocarbon molecules that split apart but don't burn in the combustion cycle. Hydrocarbons (HC) is simply unburned fuel that escaped the combustion cycle." Sounds like incomplete combustion to me, molecules that are split apart but didn't finish burning. HC is fuel that never even got started. The reality is this guy could pass with just a simple timing adjustment but we can't diagnose that over the internet. But what hasn't been mentioned is that if you look past the EGR as a problem that advanced ignition timing is also a cause for high NOX readings. This guy might just need a timing adjustment or a timing adjustment and a little carb tuning. The possibilities are endless without seeing how the car reacts to any changes. Another funny point is my chart for common emission failures shows a partially restricted exhaust system for both CO and NOX failures. Who knows?



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