Re: How to run leaner for emissions test
The main jets only control the fuel flow when the throttle plate is open.....i.e. pushing on the gas pedal. The idle mixture screws are the only way to adjust the mixture at idle. They normally control the mixture from idle to about 1/4 throttle. Since you're having trouble passing the idle portion of the test, that would be the place to start.
However, I do agree a cat could also help your problem, but it seems to be doing its job at higher rpm so I'd try to pass the test without changing it if possible. Cat's are not cheap.
1992 Ford Bronco
E4OD- B&M Stage 2 shift kit
Full 3" stainless Bassani Exhaust
32" BFG's/stock suspension
"No replacement for displacement."
"Our lugnuts require more torque than most Honda's produce!"