Ford V10 pinging

Put in super unleaded and see if it changes, if not try adding Lucas octane booster in the red bottle with super.

You may have carbon buildup on the pistons. May be time to do a Seafoam treatment.......google it.

Did you like start noticing it after a fuel stop, or after a good many miles on a full tank at the beginning of your trip.
Neil

Maybe knock sensor failure if it uses one. Should set a code.

Thanks for the feedback. It's does not seem to have anything to do with any specific fuel. It happens randomly, regardless of fuel stops. That's also the problem, it's so random that it's hard to change something (like the octane) and know if it makes a difference. On my last trip, it happened on a hill an hour and a half into my drive out and fifteen minutes into my drive home. Both times it happened once and never repeated for the rest of the drive, even under similar conditions. There are no stored codes.

PaulJ2 wrote:
Maybe knock sensor failure if it uses one. Should set a code.

+ 1 this is where I would start.

pinging is detonation and allowed to continue will burn the pistons. I have seen them with the top ring land burned through. Run a full dose of seafoam through it. If it doesn't stop soon have it checked by a tech before severe damage is done. I use seafoam regularly in all my vehicles. On my Powerstroke I fill the fuel filter with it every filter change.

This is what carbon build up looks like after it is liquified and blown out your exhaust.
I do this on my vette and tahoe twice a year.
http://i80.photobucket.com/albums/j184/gpracer1/Seafoam.mp4

Btw, this method involves sucking in seafoam liquid directly into the intake manifold, coating the intake valves and pistons. The you let it sit for 30 min before running.

check your #9 and #10 coils

I would start by cleaning the inside of the throttle body,and clean the mass air flow sensor(maf).Both are easy to do and could make a difference.

2002 to 2008.5 V-10s have two part spark plugs. I'd have the spark plugs replaced by someone who knows what they are doing with a Lisle tool to minimize the chance of them snapping on removal. Coils are well under a C-note for ten, so I'd probably consider replacing those as well.

However, it can't hurt to go with the easiest fix first -- change fuels, try Seafoaming it, and if that doesn't work, replace the plugs and coils.