85 emissions rejection

[meddle]

My 1985 just failed emissions in Massachusetts. It failed in Nox. everything else was within specs, but close. Anyone care to comment or tell me a mechanic in the Berkshire county area whose is competent?

 

[tigmaned]

they didn't give you a idea for what to look for with a high NOx reading? they do in maryland. i had a high hydrocarbon reading.

 

[Edmond]

How tuned up is the car?

That's usually the first thing I would look at. Not only will a good tune up get you lower emissions, it'll improve the smoothness of your ride and the gas mileage should go up.

 

[meddle]

Thanks; I will check but I keep her running good. I think something else is going on. I get 32 and 42 codes after 20 miles of driving.

How tuned up is the car?

That's usually the first thing I would look at. Not only will a good tune up get you lower emissions, it'll improve the smoothness of your ride and the gas mileage should go up.

 

[Edmond]

Thanks; I will check but I keep her running good. I think something else is going on. I get 32 and 42 codes after 20 miles of driving.

I don't know what those codes are off the top of my head. What are they? Isn't the 32 a lean or rich condition?

 

[WhalePirot]

High NoX is from excessive combustion temperatures which normally occur under very lean conditions, like deceleration. The EGR is electrically controlled by the ECM through a relay, using vacuum to power it open. It allows exhaust gasses into the intake manifold to reduce these temperatures and, therefore, NoX.

Your engine may be running too lean or your EGR system is not functioning properly, is my guess.

I am travelling and away from my manuals, for code decoding and the procedures for a rather simple EGR valve test using a vacuum source. I would suspect applying vacuum directly to the EGR valve would noticeably change the idle speed.

 

[tigmaned]

so what would cause a high hydrocarbon reading at a idle??

 

[grapeknutz]

Sounds as if the EGR valve has gone bad. Try replacing the valve.

 

[WhalePirot]

so what would cause a high hydrocarbon reading at a idle??

Running rich. It is reflecting unburned fuel.

 

[kalmwill]

My car also recently failed the e-test on all counts. The diagnosis by my mechanic found that the EGR valve was defective ( it wouldn't hold vacuum) and that there were a number of vacuum leaks from a number of old hoses. My spark plugs were white from running lean. After fixing the vacuum leaks and replacing the EGR valve the car was able to pass. The mechanic that did the repairs used to run a Corvette restoration business and knows the cars well. He said that the catalytic converter on these cars fails frequently. As for high Nox, it is caused by a lean burn condition, usually caused by a vacuum leak or a faulty EGR valve. Hope this sheds some light on your circumstances.
Good luck. I hope you find an easy and simple solution that isn't too costly.

 

[geekinavette]

Running rich. It is reflecting unburned fuel.

Negative buddy...

Running rich and passing unburned fuel are NOT the same thing. True, high HC DOES mean unburned fuel...however running "rich" means it's burning too MUCH fuel, resulting in high CO content possibly. While it is very likely that unburned fuel will get out with a rich condition...it's important to make the distinction between unburned fuel and running rich.

The O2 sensor is not designed to detect unburned fuel, only the amount of fuel that has been burned.

 

[jmccloud]

High NOx

High NOx can be caused by a bad EGR or O2 sensor. How does Mass. run their emissions test? If it's under load and at various speeds, high NOx may indicate a bad EGR. If it's at idle, it's NOT the EGR.
My few failures in MD for high NOx were caused by bad O2 sensors. How old is yours? If it has more than 50,000 miles, replace it.
Hope you pass.