Failed my emissions test.

[HFX]

Finally moving my residency to Georgia from Louisiana which means I need to pass the emissions test to register the car here. I took it by just to see how it would do and failed on nox emissions.

Motor is the Olds 307.

First number is reading, second is the allowed
25/25 Test
HC ppm 126 144
CO% 0.06 0.92
NOx ppm 1768 1014

50/15 Test
HC ppm 76 148
CO% 0.04 0.83
NOx ppm 1495 1100

I plan to clean out the EGR valve passageways. I hooked up a vacuum pump and the actuator is still good. Car currently needs to be fed premium to avoid valve rattle on long upgrades (which originally tipped me off to possible EGR problems after reading something from the oldsgmail list.).


I also plan to adjust the mixture control solenoid on the carb now that I know where it should be., since it is running lean (by engine feel and spark plugs). I rebuilt the carb about 2 years ago. Trash was keeping the float valve from seating properly. At the time didn't know how to adjust it beyond using a ruler type measuring device.

I'm also going to change the cat, since my vacuum seems to drop off soon after the engine starts to around 16 inches and I can't find any leaks in the lines. Compression is good, and I don't get any backfire into the exhaust. It also doesn't hesitate when I give it gas from idle like it would when I previously had vacuum leaks.

Is there anything else I should look at or adjust.

Counting the 3 more years until I become emissions exempt.

 

[85 Cutlass Brougham]

I think the EGR may be the issue as that is what is used to lower combustion chamber temperatures to avoid the formation of NOX. I would also consider something like GM Top Engine Cleaner to remove carbon deposits.

 

[joe_padavano]

I think the EGR may be the issue as that is what is used to lower combustion chamber temperatures to avoid the formation of NOX. I would also consider something like GM Top Engine Cleaner to remove carbon deposits.

The two big things that will effect the NOX emissions are EGR and converter. You're definitely on the right track to look at the EGR first, given you detonation problem. If the EGR passages are clean, replace the converter. I've used a $50 aftermarket converter (2 1/2" inlet/outlet) on my 307 and it passed with flying colors.

 

[megaladon6]

just another (less likely possibility) see what color your spark plugs are. if you're running lean it'll create too much chamber heat.

 

[HFX]

just another (less likely possibility) see what color your spark plugs are. if you're running lean it'll create too much chamber heat.

It's definetly lean. Idle is kind of rough and white spark plugs hence I'm planning to adjust the carb since I've always felt it was running lean since I rebuilt it. Well, actually first put it on it was perfect, but we didn't put in the cap on the adjustment while test driving it and it backed out enough to cause it to stall. I tried to bring it back closer, but since I didn't have the adjustment tools at the time, it wasn't easy unless I removed the airhorn again. Now that I know how to adjust it using a dwell meter and have the special tools, that is on the agenda right after I clean the EGR passageways.

Then to find my old bosche oxygen sensor while I seafoam it. I don't want to risk ruining my NKG one.

I will probably lose some of my totally awesome gas mileage, but maybe I can make it up by being able to run regular again (probably first time in 20 years).

Still can't wait until I'm emissions testing exempt so I can either put that Chevy 327 from a Impala (bad cam) or the Olds 350 (spun bearing) sitting on my Grandma's land in mississippi.

 

[Geesie]

Is it computer controlled or not?

 

[HFX]

Is it computer controlled or not?

Computer controlled as are pretty much all 307. This would make a later swap to an Olds 350 swap the easiest.

If you are going to say the computer is supposed to adjust the mixture, it can to a degree. However, if the m/c selenoid isn't mechanically in the right place, it can have trouble adjusting (or at least that is what I gathered from reading the oldsgmail mailing threads).

 

[megaladon6]

how old is the ngk o2 sensor?

 

[HFX]

how old is the ngk o2 sensor?

1 month. It was one of the first things, I changed after finding out it was running lean when I cleaned and regapped the plugs about a month ago. Getting ready to go work on it right now actually. Need to go pick up an EGR valve gasket.

 

[megaladon6]

has changing the 02 made a difference in the mixture?