It could be a timing issue. However, usually you will hear a worn timing chain. It will actually make noise in the engine. Also, usually you will get a ping when the timing is advanced. A loose chain will do the opposite.
Therefore, I would check / replace the Knock Sensor (KS). The KS is a tuned accelerometer on the engine which converts engine vibration to an electrical signal. The PCM uses this signal to determine the presence of engine knock and to retard spark timing if needed. Its goal is to keep the timing as advanced as possible for the best performance to a point right to where the engine is ready to ping.
Here is a picture of it and it's location:
I hope it is large enough for you to see. It is actually located on the rear of the driver's side head behind the steel fuel line.
Let me know if you have other questions.
Sunday, November 22nd, 2009 AT 8:47 PM