'03 F250 5.4 4x4 4R100

Today I was running alternator & battery tests which require the throttle be above 2,000 rpms for 20 seconds.

Sometimes three seconds into the cycle or with three seconds left to the cycle, the tool would get a reading of "0 rpm" although it was around 2600 rpm & repeatedly restarted the test. Tried bringing the revs higher, same result.

For some reason I was able to make it through the battery test once by switching on the heat but I'm chalking that up to coincidence.

Ever since I've purchased the truck in 2021, the rpm will drop 100-200 rpms both on the tach & audibly regardless of where I'm holding, then immediately bounce right back, generally this happens around what seems like once a minute. Haven't actually timed it with a stopwatch so I'm just going off of memories of disappointment/frustration that something else likely requires money.

Not sure if it happens it gear under load as I have to watch the road & there isn't a stretch long enough or free of obstacles/traffic where I can keep the throttle constant such as I would in park for more than a few seconds.

Does this "dipping" & loss of signal sound like a TPS on its way out or could it be something else? At 666 rpm idle, I've noticed both the load percentage & throttle seem to be abnormally high, for dead idle, both clocking in between 25-35.

 

Not sure if this is relevant but figured I'd add it in, I'm getting approximately 2.6MPG (yup, two point six) going easy on the throttle & not hauling anything.

 

I'm not familiar with a 5.4 but seems like an odd test for batteries and alt

2.6mpg sounds like fuel going where it shouldn't be. Never even heard of an engine getting that poor of mileage.

I don't have anything useful, just stopped by and thought everything was unusual and felt like commenting