engine stall opinions

Spark coils are usually overlooked because it is hard to check them when they get hot from engine heat. Most often they get checked when engine and surrounding areas are cooler.

Possibly junk floating around in the gas tank. As your going up a hill, the stuff floats to the fuel pick up line and clogs it. Once it has a few minutes to settle down, it goes back to the bottom of the tank.

In reality though, with a 23 year old vehicle, it could be one thing or a combo of several small things....dirty fuel tank, cracked fuel line, clogged fuel filter, and it all probably needs to be serviced eventually.

Start with the cheap fixes first, fuel filter and SeaFoam and work your way thru the more expensive fixes

Plugged exhaust, possibly catalytic converter, if equipped.

I had a old Pontiac that didn't like up hill driving . Found the rubber gas line over the rear end had a slice in it.

Fuel filter along frame rail under driver.

A very common failuer is the in tank fuel pump. Acts just like vapor lock. Hot days, hard climb, generator running, less than full tank of fuel.Works after cooling off. I cannot remember how many of these have been mentioned on the two rv forums I read. I had one of them myself. Took a long time to figure it out.

Swap out the fuel filter. You may even have to do it more than once assuming it keeps stalling. One answer is you have crud in your tank. When you're pulling that long hill that crud moves around.

Regardless, a fuel filter is cheap and simple to do and good preventive maintenance even if it isn't the problem. On the other end is the air filter which isn't easy to change on most F53. They seem to get overlooked often because of the PITA factor. Swap that out also so the 460 can breathe easier as it's charging up the hills.

Last cheap thing is run some FI cleaner (SeaFoam.) My 460 loves to gum up whenever it sits for awhile with ethanol gas. You may have one or more FI's that have a bad spray pattern and when it is hot it just doesn't want to ignite that pattern of gas.

Last thing might be the coil. When it is hot it has a weak spark. See if the local auto shop can test it.

All of the above is just good stuff to do regardless, and may cure your issue.

On Edit:

I now see you have a Class C, so the air filter should be easy to change unlike a Class A.

What was the engine temp when it stalled? How much fuel was in the tank? Too low of fuel, sucking air or over heating of fuel pump. Engine to hot, boiling of fuel in the line. Is it TBI(Throttle Body Injection)or is it true fuel injection(injector for each cylinder)?

Mechanics don't think it's the fuel pump. That was my first thought.
I also thought of vapor lock but it seems it would then happen when in drive also. Same with the gas line, which is something not thought of before.
I guess I'll have to see if it ever stalls in drive. Otherwise, it seems related to 2nd gear.

Bad fuel pump, deteriorated gas line, maybe even vapor lock?

Miles