Would you describe it as marbles in a tin can kind of noise?
You should be using 91 octane in this car.
4.6 motor? What is the 8th digit of the VIN?
Sounds like you are having a "pinging" situation going on. It is also called pre-detonation. There are a variety of reasons for it to happen and can cause more problems.
The detonation in the cylinders are happening before the full compression is reached.
Have you ever had any carbon removal procedures done?
There may be no codes in the computer, but would be good to check.
Disconnect the MAF sensor and drive it. IF the symptoms are gone then, I would clean the MAF sensor with electrical cleaner. There is a TSB on this.
IF not then the next area I would check is the egr passageways. Remove the egr valve and check for a build up of carbon. Using a good intake cleaner, clean both the egr valve pintle and the passageways. If there is a heavy build up you may need to get in there with more than just intake cleaner. Small brush etc. You can buy a new gasket that has a screen on it, to prevent contamination of the valve in the future.
IF this is still a problem after this, I would suggest have the PCM calibrated to the latest software version as there is also a TSB on this as well.
Sunday, January 11th, 2009 AT 7:00 AM