Yesterday I caped the Crank vent to the TB on my 01 Silverado 4.8 (already capped the PCV 2 weeks ago) and put in some new $3 Bosch platinum plugs gaped at (.072 = +20%) I am experimenting.
When I first started it up, the motor lugged and ran rough. After a few seconds I shut it off and restarted it. That time it fired right up and idled down just fine.
NOW- If the ECU can adjust in seconds to capped vacuum ports and over gaped plugs...
Why does it take a whole month of driving or more for the ECU to adjust to the groove?
My guess, it was adapting to open loop starting cond. It was re-setting the IAC, that's pretty simple for it. Fuel trims take longer, w/ adaptive learning, the short trims and other inputs shift the Long trims over time.
My 2 cents.
Tracy G
Tracy Gallaway
Founder and Constant Aide to Gadgetman
Gadgetman Reno, NV