I posted this last night in the E450 forum and JWK suggested I post it here. Here's the other post:

https://www.ford-trucks.com/forums/showthread.php?t=1540702&goto=newpost

2012 E450 5.4 214k

Back on here again, and I got another bus giving me trouble. Like my last one, first, a bit of the backstory. May seem a long story, but there may be some combination of events someone else may have an 'ah-HA!' moment. Just for the record, I know for a fact this bus does't have any diesel in the tank.

4/19/18:
Drove 250 miles over three mountain passes to the west-side to pick up this new (to us) 14 passenger airport shuttle bus. Me and a co-worker took it for a test drive. Ran and drove real nice. Only 'issue' it had was a transmission 'noise', and it only happened when I put the pedal to the floor and got the RPM's up to like 4k or more. A vibration noise is the best way I can describe it. Checked the computer and there were no codes, present or stored. While idling in the parking lot, all numbers looked good (fuel trims, temps, steady idle) and the exhaust smelled good and clean. They had recently had the water pump replaced and whoever did the work filled it with green coolant (should be yellow G-05 AFAIK).

So, on the drive home. I brought my OBD reader with me, so I set up a single gauge to monitor the coolant temp (water pump and green coolant are red flags to me) on the return trip. We drove about an hour and stopped to fill up the tank before hitting the first mountain pass. Somewhere along that hours' trip, something changed. When I came to a four-way stop, the engine was chugging. Not a random miss per-se. More like a dead hole. I figured, like all the other buses we've gotten, desperate need of a tune-up. Filled the tank and on down the road.

Now I start to notice the temp climbing, but we're also starting to climb up the first 3,000 foot pass. As it hits 210, I kick on the heater full bore. Then the back heater, full bore. Kept it at 200 max. As soon as we got over the hill and onto the flats, the temp would drop to 170, so I'd kick the heater off and it stayed around 195. I just had to replace the radiator in our other 2012 E450 (also with a 5.4, and I drove that one back last year) and the replacement radiator is a 2-core, stock is a single core. Based on what the temp was doing, $150 for a radiator upgrade was happening too (this rig will be transporting 14 workers at a time in triple digit temps with the AC cranked).

As for the power. While on the flats, power was alright. The first pass? WOW. Like, maybe 40 MPH. I kept the RPM's under 3,500 the whole way up, and that was about a half-hour pull. DEFINATLEY getting a tune-up. But, the next pass is 4,000 feet, and longer. Well...I managed to pull that pass at 60-65 MPH except for the last mile, which is what I expected. Same thing, 40. Temps climbed, heaters came on, yadda yadda.

So I finally get to twist some wrenches on it today. Set up some better gauges on Torque. Here's what I got:
LTFT1: +12% to +16% and it fluctuates quick.
LTFT2: +10% to +14% and it fluctuates quick.
STFT1 and 2: -3% to +6% and they fluctuate quick.
O2B1S1: Nothing. No voltage whatsoever. Swapped with B1S1 from other 2012 5.4 and same thing.
O2B2S1: 1.24v and flat-lined there.
Timing advance: 3 to 6 degrees.

LTFT's do NOT drop when I take the RPM's up to 2,500. I think I may have an intake manifold gasket leak...when I introduce propane around the inside edges of the IMG, the STFT's drop to normal ranges...but they stay there after I remove the propane. If I shut off the rig and fire it back up, STFT's return to the -3% to +6% fluctuation.

When I remove the air filter, STFT's dive to +35% and the engine stumbles and almost dies. I can move the filter enough to get the tip of my propane tube in and I can adjust the amount of propane to get the STFT's to normal ranges, but it still ran real rough. I can even get them to head to -15%. Still rough. No changes in LTFT's.

Fuel pressure KOEO at 55psi. KOER at 56psi. After 5 minute bleed down, it was at 35psi.

So I pull the plugs. All had some white buildup on them except cyl 2. That one had black buildup but smelled of fuel, not oil. Gap on all plugs (except #2) was at .070"+. #2 was at .060". According to the records I got when we bought this, which I didn't get until a week later, they had the plugs changed about every 40k miles. These things look like they are 10 years old.

Tomorrow I will pull a compression test on all holes, test ALL the COP's (#2 and #6 tested the same and within spec), maybe even pull the injector rails off and ohm the injectors. Think I'll swap B1 and B2 O2's and see if the no voltage follows. Maybe I got some bad wires. #2's plug is telling me I got a stuck injector (open). But the pressure did't bleed down out of spec...?

Side note regarding the O2 sensors. If I unplug them while the engine is running, passenger side (B1?) seems to kill the LTFT gauges, and the driver's side (B2?) kills the STFT's feed. I'll double check this tomorrow as well and write it down.

None of the plug wells had coolant in them (I'm replacing the intake on the other 2012 because of that).

I think they did have the intake off at some point because they clamped (with hog-ring style clamps...no WAY they got THAT tool in there with the intake on!!!) chunks of vacuum line on all the 9 factory vacuum tips (?) and put screws in the ends of them...just checked. According to the records, nobody has pulled the intake. Unless it was done before 36k and they were driving it like that for 185k.

Well, that's all I got for now. Tomorrow's coming fast.

-McMechanic