As most of u know, a smog test is required here in CA every 2 years. This is becoming a major pain.
For my latest smog test I took the supercharger off the car to make sure it wouldn't affect anything. Didn't matter, it still failed. I noticed at the shop u can smell the rich exhaust at idle, so it appears to be running rich, but why?
There appears to be no exhaust leaks, can't hear any. Does sound like a misfire at lower rpms so I was thinking maybe one of the plugs or wires, I guess I will change those out first. Motor runs strong at upper rpms.
Stock fan temperature. I did pull the #1 and #3 plugs really quick, they looked perfect tan color.

Here are the numbers:

@15mph: HC=66 (max=58); CO%=0.39 (max=0.34); NO=108 (max=586) fail
@25mph: HC=66 (max=34); CO%=0.43 (max=0.32); NO=170 (max=706) fail

Results from 2006, same motor except fans:

@15mph: HC=27 (max=83); CO%=0.03 (max=0.48); NO=236 (max=689) pass
@25mph: HC=27 (max=48); CO%=0.03 (max=0.46); NO=243 (max=706) pass

for the 2006 test, the fans settings were much colder than stock

Notice how the max allowable emissions have been lowered since 2006. The smog techs told me they are lowering them again this month. I don't know if that's true or not.

Thanks for any ideas which could be the problem.

 

Maybe you need a new cat.

 

I'm surprised at the lowering specifications....it's only reasonable to assume that a car can meet the fed standards for the year it was manufactured. Check to make sure your shop is doing the right thing....

In any case, when HC and CO are high, the second place to check is the catalytic convertor, the first is to do a good tune up...plugs, wires, fuel filter, etc.

Good luck!

 

High HC and CO, with low NOx is typically due to running rich. How old are the O2 sensors? How hot is the coolant when they are running the test?

 

Mr. Injuneer,
Yes i know it is running a bit rich...u can smell it.
I believe it will pass when I find the problem making it run rich. Hopefully I will find it without replacing a lot of stuff.
The O2 sensors are the original units.
The coolant temp gauge reads about in the middle when the car isn't moving, so I am guessing 220 deg. The fans then come on. Stock fan settings.
My car has only 60K miles on it. Hard miles though.
I am going to hook up datamaster to see what the computer is doing. I read on another post about swapping O2's from side to side to see what happens.
I am probably just going to get new O2's anyway. Are the factory replacements okay or should I just get the originals? I saw a replacement set on ebay for $100.

I also recently purchased an Innovate LM2 for another vehicle, it has a wideband O2. I could hook that up and see what the actual air-fuel ratio is.

 

Swapping them side to side isn't going to prove anything. You have 16 year old sensors. Replacing them would not seem to be an unreasonable attempt at a correction. DataMaster will tell you if the long term fuel corrections are elevated, and that would possibly point to a "false" lean condition.

You want the AC Delco/Delphi replacements. Shoebox has the part number on his website.

 

Just a follow up on this guys...
After taking off driver side valve cover, I found some problems on a pair of pushrods grinding into the guide on the #1 cylinder.
After removing the intake manifold...
I found 4 comp cams R lifters in which the retainer was missing, so this messed up the valve train geometry and made it run rich at low rpm, this is my theory.

The cats were eaten up, instead of the "brick" being full length, it was only about 2 inches long. Both cats were damaged due to running rich. I decided to remove the flp long tubes (they will be for sale soon) and install mac shorty headers with a new LT1 magnaflow CA legal cat. I am also going to weld on a bung for a wide band O2 sensor to make sure its running correctly.
The lifters have been replaced with new gm parts.

I will post the smog test results in a few weeks. I expect it to pass with flying colors now. BTW, blower is disconnected for now, just going to run it as a daily driver NA.

 

Good luck, I failed the first time and barely passed a second time on a 15k mile engine with nearly everything new.

 

Hi guys, just following up on my initial post....

I ended up replacing all the lifters with LS7 (found 4 bad ones, comp cams), took the blower off the car, new 30 lb injectors, modified fuel inlet to injector rail, new plugs, mac headers, dynomax turbo muffler, new cat.

I ran it around for about a week and hooked up a wideband o2 sensor on it. It seemed to be running a little lean but it was hard to tell.

Took it in to smog and it PASSED! Man was I happy about this .

Here are the results:

At 15mph
HC=14 CO=0.00 NO=298
At 25mph
HC=22 CO=0.09 NO=171

I was running 42 lb injectors with the supercharger, but when I swapped to 30's i didn't even change the computer, it was able to compensate for them.
It runs great now and I just love that muffler, a lot quieter than before but still a nice rumble at idle. My mileage has increased a lot since disconnecting the blower, from about 150 miles per tank to 200. Perhaps someday I will reinstall it.