Corolla noisy when cold

I have a 2003 Corolla with 143,000 miles. When I start it in the morning it rattles like crazy. I took it to my mechanic and he said it's coming from the cam. He thinks it's either a worn cam or clogged oil journals. He said he does not recommend trying to clean the journals or it could cause the clog to move which will lead to engine failure. At some point I plan to have him take a closer look, but I was wondering if anyone had any thoughts on this problem. I've been driving Corollas since 1980 and have never had this problem.

Thanks, Smitty
I have a 03 which knocks until it gets warm, especially in winter. Its been doing that for years. Its does it when i accelerate, but not at idle. It may not be normal for newer car, but I consider it normal for mine and I have 268,000 miles. But I would not describe it as a rattle. Have you found reason for your noise?