So, what exactly is the PCM "learning"?

For the first tens of miles, up to about 100 miles, of driving, the engine sensor outputs are recorded. This will be the baseline for the computer to consider your normal requirement of throttle response, shift points, and loads on the drivetrain.

If you baby it, then the system will perform to that level.

If you are very aggressive in your driving during this period, but, you normally are a smooth operator, the vehicle will be more aggressive in it's response, after that aggressive baseline is established.

If you share driving the vehicle with someone at the opposite end of the pendulum then one of you will be a bit unhappy driving it.

OK..very basic terms.. We just replaced the battery in our 99 Ram.. For the first 5 or 6 starts, it wouldn't idle and stumbled on hard acceleration.. After several short trips, the truck ran and idles as before..

mac

Please remove splinters before emailing

IIRC this is not limited to any specific distance or time, but is a moving average. That is, it keeps learning and adjusting all the time.

Maybe your IAC is dirty.

No idea what an IAC is, but after driving the truck a while after replacing the battery, it runs great..

mac

Please remove splinters before emailing

Idle Air Controller, FWIW... Controls idle.

Oh.. nothing that complicated.. Battery died and it went without a battery until the next shopping trip to the States.. about a month..

Put a new one in from Wally-world on their free exchange deal and the truck runs fine now..

mac

Please remove splinters before emailing

My '99 RAM Van acts exactly the same way whenever the battery is pulled. It refuses to idle and I have to hold the pedal down to keep it from stalling. I let the pedal off gently and goose it when it starts to stutter. After 2 or 3 minutes of this it "re-learns" how to idle and runs fine hot or cold until the next time the battery needs to be disconnected.