My 89 745 T wagon just failed the Calif. emissions test just now. Car has 75K on a 93 motor, with 140K on the car. At 15mph, car measured 130 ppm HC's against a max allowable of 112, and CO was 2.56% against a .72% allowed. At 25mph car measured 127 ppm HC's against 86 allowed, and 2.47 CO against a max .60%. New(er) engine was put in last April. At that time a new 02 sensor was put in along with all new vacuum hoses, oil pump, and rebuilt turbo. Plugs and wires are 2 months old. Car runs and idles great, and delivers a steady 20-21 mpg with 50/50 city and freeway driving.
Looking at the numbers, archives, and FAQ's the car is running rich. Injectors are the ones that came with the 93 motor, which were cleaned and balanced. Maybe I need to use the ones (357's) that the car came with? Also the cat is the original, and 2 years ago with the old motor I barely passed the Nox part of the test. Nox measurements today were 766ppm against a max of 778 at 15mph and 428ppm against an allowed 717ppm at 25mph. My mechanic and the smog guy said that as HC's and CO drops Nox will go up, so if I pass HC and CO, I could fail again on Nox. I may need a cat. Tuesday my mechanic will do an all around check for any problems and see what he can adjust.
Will adjusting the AMM make a difference, or does it only control mixture only at idle? Could the cat be responsible for high CO? What else can I check myself before Tuesday? I will replace the air filter and clean the throttle body this weekend.
Note the max speed tested for is 25mph, probably higher than the average freeway speed during morning and evening rush hour commutes in LA.....