Do homemade CD's only work in certain cars?

Yes, some car CD players won't play home-burned CDs. Here's a tip: If you're not doing so already, use CD-R's instead of CD-RW's. You can only burn CD-R's once, but for some reason they seem to work better in car CD players. My 2001 Grand Prix CD player won't play CD-RW's but it will play CD-R's.