I have a 460 ford E-350 (motorhome)that will stall on occasions and only when it is warmed up. The engine will start and run great at first but after 2-100 miles the engine will stall when slowing to a stop. It starts right up after the stall and will drive again. In a either a few minutes or miles the stall can happen again or will keep driving to my destination. Also after sitting the stall will be gone till the next trip. After stalling the engine will start easily but idle rough. When in stalling mode once the rpms are up above 1K the engine runs and accelerates great. Going up hills is not a problem. Last year I had some work at a shop for other problems. They replaced; EGR valve, plugs, computer and fuel filter. The fuel pressure is 32 at the rail (42 when pressure regulator is dc). The egr valve operates with a vaccum activation. I have a vaccum gauge in the cab indicating good steady vaccum when driving. Also there is a code 334 (EVP sensor is/was high-EVR) pulled. I'm not sure if the code is significant. Any suggestions?
You might have a failing Idle Air Contorl Valve, IACV.
It keeps the idle steady when engine load changes and I am sure they get a good workout in a motorhome.
The other possibilities are carbon depositis and sludge buildup. You can make sure your fuel filter is changed, if applicable externally, and that you run a can or two of quality fuel system cleaner. BG44K is about all I will recommend as there is nothing else that works as well. Two cans will clean a motor and fuel system right up. During this time period the engine may behave stragnely as deposits are removed and passades get temporarily blocked or cleaned out and deposits make their way to the oil pan or out the exhaust. It is a good idea to change your oil one tank after the last can of BG44K, which will be one can per tank so the third tank of gas you will see improvement and your oil will get dirty from all the deposits removed.
You could also have other issues if this does not solve the problem. I think since it is intermitant and on warm up this is the right place to start. If issues still persist I am going to give you a walk through diagnostic for engine stalling situations. When it talks about pulling codes, your vehicle is an OBD 1. This means it is not always as easy as hooking up a reader. However Advance Auto ro Auto Zone will do it for free if it is something that can be adapted which is often the case. Then if you need electrical components tested or tools for testing, they also will test components for free and they loan out specialty and test tool kits.
Just use the link below;