When battery is disconnected, the engine computer needs to relearn and during this period, you might have performance and idling issues. A little driving should solve the problem but if the alternaotr is bad, it is not going to work.

Answered by KHLow2008 (expert)
39,900 answers provided

i buy a new battery and 2nd hand alternator(the alternator is working) after that my rpm goes up and down sometimes the RPM is working after a few seconds it goes up and down again."is theres a problem in the computer box,rpm sensor, hose or wirings??"tnx sir

Response from Edzelle
1 question asked

Let the computer relearn by going for a drive around. It might take a while before it relearns and during this period it can act funny while idling.

Lets start with this first if problem was not there previously.

Ig the Maklfunction Indicator light is showing, get a free scan done at parts stores and let us know the EXACt trouble code.

Answered by KHLow2008 (expert)
39,900 answers provided