for the past month or so when i had a cold start at night time the rev is going lower than normal

and the rev drops every 2-3 sec to 600rpm, and the dash light is dimmer too, wondering if my alternator is going out?

then i try to drive hard for a few miles and then it's going alright again

my car has 55k miles and 4 and half years, so maybe time for new alternator or battery?

 

Chances are is that it is the battery. IF it was the alternator it would not get better because it wouldn't produce any juice.

 

sounds like your battery to me, do you still have the original battery in your car? batteries normally last roughly 5yrs, so that is probably the problem. get an optima and be done with it.

 

If it was the alternator, then it wouldn't charge the battery. But this is the opposite. So I would imagine it's your battery. It's not holding the charge well, so it's harder to start up, but once it's running, the alternator is charging it.

Get the battery tested at your friendly local auto parts store.

 

Don't waste time getting your battery tested, just replace it. At 4.5 years, you're living on borrowed time.

 

i tested past monday and it was fine

but now it's getting worse, going to check again tmr

i need to pick up my girl from london tmr so i need to make sure everything is good b4 i go

 

Ditto --- I agree