Idle Problem after battery replacement

[TCV]

The battery on my early '93, 3L Ranger went dead after sitting four hours. The alt charges, battery tested good but almost dead. After a recharge, I reinstalled it. Now, the engine idles so slowly that it often dies. The IAC valve is only a year old. What could be the problem?

 

[90longbed]

over time the computer makes adjustments to fuel trim, timing etc etc.... when the battery is disconnected it resets it to the factory pre programed peramiters..... just take it for a good drive and drive it as you normally do and it should correct itself

 

[RonD]

I would recheck the battery and alternator.

Engine off, key off, charged battery voltage should be above 12.4v
Below 12.4v means battery is failing, it will hold a charge but not very long.

Engine running at idle, voltage at battery should be above 13.6v, at least 1v above battery voltage is needed for charging.
Turn on all the lights and heater fan to high
Voltage should drop then come back up to at least 13.6v, voltage regulator is working
If voltage is lower then 1 or 2 fields in the alternator are not working, there are 3 fields that provide power.

Raise engine RPM, voltage should go no higher than 14.7v
If higher then regulator has failed and alternator fried battery, replace both.