When I start my truck when its cold, the throttle response it almost instant.. but its only responsive during the first 10 sec or so when it is idling around 1800rpm. then when it goes down and settles at regular idle its back to normal.. What causes this, Different a/f ratio at cold startup?????

 

Cold start stratigy goes like this.
At key turn on, the PCM looks at the values of the ECT and IAT sensors to determine the amount of extra fuel to inject (pulsewidth) and what to do with ignition timing and IAC opening position. Open loop operation.
With the IAC open to a large degree, this makes the idle go high until two things happen. 1. a timer is invoked to slowly bring down the idle speed. 2. while the Ox sensors are heating from hot exhaust gases along with their built in heaters.
Once the Ox sensors get up to operating temp about 600°, the PCM will accept their signals and begin to control the injection pulsewidth at leaner values. Closed loop operation
As for throttle response, it's the same as any motor responds to.
When in that warm up period, there is higher air density being drawn in before the intake and heads get a chance to heat up and reduce the density as well as some ignition advance applied.
You percieve this as a good deal extra power from these conditions until the motor heats, the ignition is retarded and fuel richness is cut back.
Thats just the way it is once the thermostat begins to open from a 200° motor, all this nice extra power goes away.
Obviously the motor can't continue to run in the cold start conditions at any other time.

 

Just in curiosity, would what happen to the engine if you had it parked on a straight road overnite and right at the second that you go to start it, you slam it into drive and floor it?

what damage would come to mind???

 

oh man, i dont even want to think about what kinda damage would result in that. I would hate to be that motor or even the driver when that happens.