I had a similar problem with my 2000 Avalon XLS around 170,000 miles.
If you open the hood and look at the battery, there are positive and negative cables connected to the battery.
First check you should disconnect these from the battery and clean them. You can buy a small wire brush battery connector cleaner (looks like a small Christmas tree)
that has a pointed end for cleaning the cable connectors and then a hole with brushes inside to clean the terminals on the battery.
Just place it on the terminals and turn back and forth until most of the residue (if any) comes off.
For me, this improved things but didn't solve the issue. What was really happening is that I had corrosion built up on the cable where the connector terminal was connected to it.
If this makes sense, I am talking about the small crimped part of the connector terminal that is squeezed around the wire that leads down into the relay box, etc from the battery.
I tried cleaning this with different tools and they all failed. My options were to replace the cables and terminals which was a pain, or to try an old farmer recipe used on tractors and other things that get corrosion build up in hard to reach locations. So, I went with that. Which was (in all seriousness); grab a 20 oz can of Coca-Cola (the regular kind) and unplug the connecters from the battery completely. Pour the coke all over the battery terminals, the connectors and of course the crimped part of the connector where I had the corrosion that I was struggling to remove.
Within about one minute, all the corrosion was completely gone and my car has been running perfectly for the last 20,000 miles. Amazing what a can of coke will do. Also, it is fantastic at taking motor oil or similar off your windshield if it gets thrown up there by trucks etc. I'm really not joking even though it sounds ridiculous.
Saturday, December 15th, 2012 AT 7:55 PM