Hi,
My car is a Camry 90'(4 cylinder, automatic trans, 110k miles). Two
months ago, it began develop a noise when cold start, especially in
morning. The engine sounds no more smooth. After driving several miles,
I cannot hear it anymore. The noise is a little like metal strike,
although it is absolutely not sharp. All and all, I cannot describe it
more clearly. I once drove the car to a garage one hour earlier in
order the car was cool enough and the technician could hear the noise.
But the noise was not obvious then. The technician could not find
anything wrong. For me, I feel the engine does not sound smooth than
two month ago even when the car is hot now. The technician didn't think
there was problem though.

The timing belt was not changed before. From the newsgroup it seemed
that worn timing belt may cause this. Unfortunately after changing
timing belt and water pump, the noise is still there.
Somebody in this newsgroup mentioned knocking sensor to cold start
noise. Although I have the Haynes repair manual, I cannot find the
sensor. If there is a knocking sensor for 3SFE engine, where is it?

What can I check for the noise?

Thank you very much.