Ok I've got an '81 GS with all the emission crap intact. I just had a brand new cat converter installed and It failed. According to them the car is running too rich. It failed CO at 25mph And HC at 15 and 25mph. Everything else was perfect. However it was right after the exhaust was done and the exhaust smelled really funny. How can I fix this because I'm so close to passing.

 

Ok so how do I lean out my fuel mixture?

 

More air or less fuel. Only way to get less fuel at test speeds (not idle) is to change the jets in the carb. To get more air, you could induce a vacuum leak.

Odds are the best way to pass is to make sure your air pump is connected and pumping air into the exhaust stream just ahead of the cat all the time. Connect the output of your air pump through a check valve into the exhaust. If its truly stock that should be running through a valve on the carb (the ACV), you want to bypass that entirely so that its on all the time.

 

See its an aftermarket cat with no tube for the air pump. However my choke had stuck open earlier and I think I unstuck it but maybe not all the way. ?????

 

Heres what I got.

%CO2 %02 HC (PPM) CO (%) NO (PPM)
Test RPM meas meas Max Ave Meas Max Ave Meas Max Ave Meas
15mph 2078 13.2 0.0 309 58 438 2.90 .22 2.88 2488 607 75
25mph 2234 13.1 0.0 289 36 419 2.45 .13 3.19 2288 388 68

Can anyone interpret this?

 

Yeah... but its to tell you what you already know... yer running pig rich. Find out why and you've got your problem. You say its stock? Have you gotten it to pass a test in the past?

You say that your choke was stuck... that'll cause it to be rich. Did you recently notice a big drop in gas mileage?

 

you need to have a cat with a air pump, so the cat can burn up the extra fuel, or you are going to melt that cat in no time.

 

You should be able to drill a hole then solder/weld/epoxy a bung (hehe thats a funny word, BUNG) into your exhaust just ahead of the cat flange and hook your airpump up to that.

As I understand it, the cat takes care of the hard work of the emissions. The rest of the emissions stuff on the 12a exists to keep the cat from burning out and blowing up. So you need that airpump and some of the rats nest goodies to keep that new (expensive?) cat alive.