Piston slap.......... It's typical for a 4.6. The piston to wall clearance at cold startup allows the skirt of the piston to rock a bit. As it warms up, the piston expands slightly and the noise goes away.
Quite a few 4.6's have the same thing going on. Switching to 5W20 helped mine quite a bit.
Oh ok, I also think that it might be the pulleys because they are the chrome ones, I'm not really sure. Car runs good and everything. I'm going to try 5w-20 oil and see if it helps. The car have a little over 100,000 miles.
It is normal for the 4.6 to make noise from the timing chains at initial start up. The timing chain adjusters are contoled by oil pressure.
The noise should stop after 1-2 seconds when the oil pressure builds.
If the noise is from the timing chains, it will be much shorter on restarts. Try this. Start the motor and let it run for 10-15 seconds. Turn it off and then restart. Normal timing chain rattle will not be present on the restart because the adjusters will already be pumped up.
Also, if you want additional assurances, get an oil filter cutter and cut and inspect the oil filter at each oil change. Look for small bits of metal on the filter element. I now do this with every oil change. It likley would have prevented the motor failure (timing chains) if I had.
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