sandersd said:
I am having the same issue! Ford only allows you to use regular unleaded for the Ford V10. Ford uses a knock sensor that reads the engine and adjust the timing. Warranty is voided if you use anything but regular unleaded. At 55-60 mph when traveling on a flat road I don't have the noise but when I hit a hill or have to pass the noise returns. Engine performance is not hindered. Has anyone had this diagnosed?
I'm curious what you mean by regular unleaded. If, by that, you mean 87 octane then the 2017 E-series owners manual actually calls for a minimum of 87 octane but a recommendation of 91. The 2016 F53 owners manual says the same thing. In 2000, they specify 87 octane, but (a) you're way out of warranty on anything older than a 2016 by now and (b) I would be interested to see any case where they successfully defended against a warranty claim where the owner used a higher octane fuel than was recommended. Lower octane - absolutely a problem, but you're not going to cause any problems at all with a higher octane fuel.
What year engine and what chassis are we talking about here? Earlier motors were prone to having spark plugs loosen up due to aluminum heads with only a couple threads for the plugs. A plug that's getting loose sounds *exactly* like lifter (or in the case of a pushrod engine, rocker arm) tick. One of the things that all the Triton motors are somewhat famous for are the exhaust manifold studs breaking. When that happens you get an exhaust leak and that will almost always sound just like rod knock. It's a good way to get a cheap truck if you don't mind spending hours screwing around with extracting the old studs! In my own experience it doesn't seem quite as common on the 10s as the 8s, but that might just be a sample size problem.
Personally, I would go up to a 91 or 93 octane fuel and see if that cures the problem. If you wanted to get sciencey about it, you could pull and log the live OBDII data and watch the spark advance to see if it retards when you're hearing the noise. It's not a perfect test because knock sensors can get fooled, but my guess is that you would see it pull timing a bit until the clattering stopped and then it would advance it back out.
Or you can run it real low this one time and then fill it up with 93 and see what happens. If the noise is gone, there's your problem. If not, my money would be on either exhaust studs or a loose plug.