Under the hood: What’s causing my motorhome’s engine to surge?

We have a 2004 Ford E450 class C 23-foot motorhome with the V10 engine. It just turned 45,000 miles this week. We did a 500-mile trip this past weekend down I-5 to Medford, Ore., and return to Tillamook, Ore. Pulling long grades the engine surges mildly as if it's running out of gas. Switching out of overdrive helps some, but the surging returns to the point I back off the throttle and accept slower climb to the top. On a 1 to 10 scale it's only about a 2, at worst a 3. O'Reilly Auto Parts did a code scan and found nothing stored. Are there really two fuel pumps in series? Is there a second fuel filter different from the one inside the frame rails below and slightly behind the driver's seat? Is there some way a human being with normal limbs and joints can access a fuel rail test port? Do I need to pull the doghouse from the interior? It's never been out so far. I've read that some COP electrical connectors occasionally back off causing misfiring. Is this common? Is my next step installing a pressure gauge on the fuel rail, and watching it while driving under different loads?

Here are answers to your questions: No, unlike the earlier Ford motor home E350/450 cutaway chassis, there is only one fuel pump, which is located in the tank. There is a sock or strainer prior to the pump, in addition to the frame mounted fuel filter.

‘It has a coarse weave to stop larger particles. A fuel pressure test port is thoughtfully included on one of the fuel rails atop the engine. Connecting a fuel pressure gauge, such as the OTC 5630 or similar, requires removal of the engine cover, also referred to as the "dog house." (Be sure to follow published safety procedures!) I'm not aware of ignition coil connector problems, but they are known to sometimes leak spark due to faulty insulation. Observing fuel pressure while driving is a good diagnostic strategy, but there's an easier/safer way to infer proper pressure, using an inexpensive OBD-II scan tool such as the Autel AL519 or similar. Monitoring the "short and long term fuel trim" will indicate fuel system abnormalities. Ideal fuel correction is within a few percentage points, positive or negative, from zero. A strong positive indication, such as +15 percent or more during a hill climb indicates a shortage of fuel. Depending on conditions you may see this in either short or long term trim, or both.

Typically a misfire or severe fuel issue will result in a check engine light and code set. Your situation may be a bit mild for this to occur. I'd also try using the scan tool's "Mode 6" to look for misfires specific to a certain cylinder. If a cylinder is misfiring, try swapping the ignition coil with a neighbor and re-check to see if the misfire followed the coil!