Battery problems.

[nefarious986]

Hey guys,

My battery died yesterday and left me stranded. I paid for a jump ($55 from AAA) and got the car back home (45 minute drive). This morning it didn't start again, so I walked to Kragen and got a new battery. Its an Autolite 48-84.

I thought 48 was our battery size, but this one was physically a bit smaller than the OEM battery. They didn't have one exactly the same sized as ours, but the guy looked it up though, and said this should work for the car.

Now its installed and cranks, but at idle, the car is not staying at the same RPM. Before, it usually stays at 800rpm flat, with no movement on the needle, but now its fluctuating down to about 600 and then revs back up to about 900 automatically and then drop back down to 600. This would happen constantly.

Car ran strong yesterday after I got the jump start, but haven't been driven since I installed the new battery. The fluctuation rpm worried me and I turned it off after the car idled for about 3 minutes and didn't get better.

Did I buy a bad battery or the wrong battery size ? Or could it be something else ? Should I take it to a shop ?

Thanks.