Failed Smog Badly, need help.

sd_iconoclast

Registered User
I have an '89 SC and I just failed smog badly, and I have no idea where to look. I hope that one of you guys can give me some ideas.
It failed on HC, CO, and NO although it seemed to fail the worst on NO.
I have attached the results.
Here are the other symptoms:
The car runs great, although it seems to use a quart of oil every month.
It seems to run hot on the freeway.
My speedometer frequently stops working while on the freeway. I don't know if that is related.
Your suggestions would be appreciated
 

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HC is unburnt fuel .. need to make sure your ignition system is in good order.

NOX could be high from an inoperative EGR ( if you dont have it, the engine temp is the main factor ) .. or the fact that the engine runs too hot will produce NOX - Nitrogen and Oxygen.

The CO is supposed to be a product of the burnt fuel Carbon combining with Oxygen, but your Catalytic converters should be turning it to CO2 by combining the Oxygen from the NOX ......

Speedometer has no effect on these numbers.

Get your engine to run cooler. And you may possibly need new Cats.



- Dan
 
I thought that mybe the high NO and high engine temps on the freeway point to innoperative EGR, but I can't understand the high CO and HC too.
Is there any one sensor that can cause this?
 
Egr not working/plugged up, a tune up, possible lazy O2 sensors.....and looks like your cats are dead

How well is the idle quality? Does it buck/pop/fart on the highway? The high hc is usually a sign of ignition issues...but hc will follow co if its high. The key is you have high do and have left over O2.
 
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With an EGR delete, and both my o2 sensors inoperative and a vac leak, I passed emissions. I failed the first time, so new filters, plugs and wires, and a bottle of Lucas "tune up in a bottle" fuel treatment, I passed. An ex chief mechanic for 20+ different formula race teams also added, unscrewing the oil cap/drilling a small hole and unseating the dipstick temporarily, and adding alcohol to the gas will help slip it through emissions. He's familiar with these cars, and jack of all trades, and unlike the saying, master of them too. He was my hang gliding instructor. Quit cars because he wanted a less stressful job lol
 
I thought that mybe the high NO and high engine temps on the freeway point to innoperative EGR, but I can't understand the high CO and HC too.
Is there any one sensor that can cause this?

NOX is produced at high engine temperatures .. EGR in effect does cool down the combustion chamber and decreases the amount of fuel entered into the system, but it does not Cool down the engine itself - if your engine runs hot, you will fail on NOX. You can check EGR operation with a vacuum pump to the EGR valve and if it stumbles or dies, the EGR itself is working or not clogged up - wether the PFE sensor is working or the EVR is operating is another diagnostic you would have to follow .. but typically the PCM would set a Check engine light or a code when it does the Comprehensive test of its components unless the PCM itself has failed on these circuits.

High HC could kill your catalytic converters, but the reason for the high HC would have to do with one of the air/fuel monitors, ie. O2 sensors, MAF ..

Im assuming you have no Check engine light or codes coming up - and the engine itself is relatively stock.


- Dan
 
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Here is more info that I forgot lat time:
1] I replaced the spark plugs and O2 sensors just before the test.

2] When I say the engine runs hot, I do not mean that it overheats, it just runsd alot hotter than it did before this started. I have a 180 degree thermostat and a separate fan controller set for this lower temp, so I used to cruise aroujnd at about 200 degrees. Now I am around 225.

3] I am not exactly stock, I have a 10% OD pulley, aftermarket throttle body and 42 lb injectors with new MAF sensor tuned to them. But I have passed smog several times with this setup.

4] The ECM is throwing no codes

What is the PFE sensor and EVR?
 
Here is more info that I forgot lat time:
1] I replaced the spark plugs and O2 sensors just before the test.

2] When I say the engine runs hot, I do not mean that it overheats, it just runsd alot hotter than it did before this started. I have a 180 degree thermostat and a separate fan controller set for this lower temp, so I used to cruise aroujnd at about 200 degrees. Now I am around 225.

3] I am not exactly stock, I have a 10% OD pulley, aftermarket throttle body and 42 lb injectors with new MAF sensor tuned to them. But I have passed smog several times with this setup.

4] The ECM is throwing no codes

What is the PFE sensor and EVR?


The PFE monitors exhaust pressure for the EGR to the PCM, and the EVR electronically controls the vacuum to the EGR.


- Dan
 
NOX is produced at high engine temperatures .. EGR in effect does cool down the combustion chamber- Dan
Sort of. Its high combustion temperatures, not engine heat.
Typically high mileage engines with carbon build up will do this as the carbon deposits heat up and act sort of like a glow plug. The way to tend to this is, of course, to remove the carbon build up. Thats what chemicals such as seafoam do.
 
Sort of. Its high combustion temperatures, not engine heat.
Typically high mileage engines with carbon build up will do this as the carbon deposits heat up and act sort of like a glow plug. The way to tend to this is, of course, to remove the carbon build up. Thats what chemicals such as seafoam do.

yup agreed you would have to run that engine pretty hot in the coolant dept to increase the nox the way his test looks. being the car failed all three I would suspect that the cats are completely dead. if you were rich or something like that you would have low NOX due to the fact you are making a fairly cool combustion chamber with all the un burnt fuel and such. NOX is from high cyl temps from running on the lean side for efficiency. lean mixture means high cyl temps and thus high NOX.

stupid question did you warm the car up before taking the emission test? or did you start the car and drive a block to the test station and fail. you might need to get the cats very hot being they are old and probably not very efficient and burning all that oil doesnt seem to help them at all either.

look at the O2 sensor readings, they are below 1 percent that indicates good combustion, if there were a misfire the o2 would be higher. Also notice how it cleans up with RPM (adding heat to cats). I belive its a mix of the burning oil, and bad cats if indeed the motor is running good but 02 indicates it is.
 
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I am guessing you have a vacuum leak, which is causing the O2s to dump fuel to get the mixture correct, which is raising your emissions at idle well past the maximum permitted amount. And off idle, it's still there, but a smaller percentage of the total air demand, so it is closer to passing.

It would be instructive to see your fuel trims and commanded spark timing under these conditions. Do you have a tuner?
 
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