This may be a long read, but I'm going to be a thorough as possible. I'm at my wits end on this...

This is a 2003 F150 Supercrew FX4 with the 5.4. About 215k on it currently.
To start this all, last year my a/c compressor locked up. So I bought a replacement, and decided to do the timing set while I was doing it. (Ok, I didn't do it, a mechanic friend of my father did). Replaced the guides, chain, tensioners. GOt the truck back, it ran like CRAP. The guy took it back apart, asked me to buy new plugs and coil packs, and said it was fixed. Still ran like dook. Horrible valve clatter, no power, etc. I suspected it was off 1 tooth on the driver side, and low and behold, it was. SO, after that was fixed, it ran like new again. Few months passed, I noticed a coolant leak. I traced it down to a faulty intake manifold. So I bought a new one, and replaced it. I'm not very confident in my ability to work on the mod engines, but I took my time and everything went smooth as silk. ALso noticed the knock sensor wire was rubbed in half. so I replaced it while I had everything apart.
Everything was going great until just a few weeks ago. I noticed that when the truck warmed up, it would seem to lose a gob of power. It was gutless pretty much. I'll describe it best I can. If you were starting off at a dead stop, when you accelerated, 1st gear felt fine. Pulled good. When it shifted into second, you could feel it start to pull, then it would fall on it's face. Like a weight sled was hooked behind it. No matter how hard you pressed the accelerator, if you feathered it, whatever it would just drag along until suddenly, all the power would come back! Ok, so this has been dragging on for a few weeks now, and I"ve been monitoring everything with Torque PRO to see if I can find the culprit.
So with torque pro open, I started watching the spark advance. WHen the engine is cold, spark advance rarely falls below 11*. Truck runs just like new. When it gets warm, when you first start from a stop, in 1st it starts out around 11* then maybe does down to 7* right before it shifts into 2nd gear. 2nd gear hits, it falls to 3* sometimes down to 0* or even to -9*. Thats when it feels like a slug. You'll keep accelerating and then it jumps back to around 11* and drives fine. So I added more gauges to my screen to see if it would show anything.

This is where it gets weird. I have some little cheap generic bluetooth adapter that I use to hook to torque pro, and I kept seeing "Bad data from PCM" pop up at the bottom of the screen randomly. Didn't give it much thought because, ya know, cheap adapter. SHortly after when I had the live monitor going, I'd hear something talk for a few seconds, but couldn't pinpoint what it was saying. Come to find out, it was my phone (turned way down) saying "ICY CONDITIONS). I couldn't figure out WTF was happening until I actually saw it. Truck fully warm, the IAT would be at say, 95*, and usually stayed anywhere from 5-10* hotter than outside. It would randomly drop to 10* and then right back to the correct temp in just a flash. Or, it would randomly peg out at 190* and then fall back to normal. I figured bad IAT sensor, but didn't change it just yet... I started keeping a close eye on the fuel trims, short term and long term. THey are doing the same exact thing. The STFT fluctuates btw -3.1 and +3.1 normally, on both banks. LTFT on Bank 1 is usually +4.7 at idle, and moves according to rpm. Bank 2 stays close to 0 and moves based on rpm. But they all will randomly either bottom out, or peg out for a split second, then return to where they normally reside. I watched the TPS yesterday, same thing. Cruise set at 65mph, tps showed 38%. All of a sudden, it jumps to 90, then settles back to 38%. The truck doesn't do anything because it's so quick you have to keep a sharp eye or you'll miss it. It idles fine, has no vacuum leak (i smoke tested it twice), a new PCV valve, MAF sensor, I've cleaned the throttle body, and like stated before it has new motorcraft plugs, new coil packs, new intake, fresh fuel filter. new timing components, new DPFE valve, and new knock sensor.
I thought the cats may be stopping up because Im hearing noise out of the driver side cat... its not a rattle, it's more of an...exhaust sound. Like the sound of exhaust moving through a header collector (if that makes any sense). There's no exhaust leak that I can find, and it doesn't even sound like one. I'll describe it one way I know best. If you watch the Dukes of Hazzard, during a scene where they are in the car driving and talking, you can hear the "exhaust" in the background. I don't know how to describe it, it's weird. Anyway, so I checked the temps on the cats with my infared thermometer. Fully warmed up above the pre-cat, temp is about 400*. At the pre-cat exit, going into the secondary cat, temp rises to 460-480*. Then at the exit of the second cat, the temps are about 340*. Everyone's told me that means they are clogged, but since this is a 2 cat system, I'm not sure what the temps should be.

I stopped by a friend of mine's shop on the way home from a work trip Friday so he could hook his Snap On scanner to it and see if he saw anything that I couldn't. He read everything, saw no misfires, nothing funny and then the PCM kicked him out! He tried re seating his bluetooth adapter, plugging it with a cable, everything. It kicked him out and he wasn't able to get back in until he cycled the ignition. I'm not sure it fully let him back in because he was puzzled with it at this point. He suggested maybe a bad PCM? Maybe a circuit board with a circuit slightly going open? That was his only guess based on what he saw and what I've told him, which is exactly what I've typed above.

I have a parts truck I can get the PCM out of, and another buddy with the software capable of programming the PATS and all to my truck for it, he also has HPTUNERS and wants to monitor it for a couple of days.

BUT before I start the PCM swap, any other suggestions? I've read and read and researched, and checked every single thing I can possible think of, or that the Internet suggests. I may have even forgotten some of it. But, anyway, short of replacing the PCM I'm out of ideas. Only thing left to check is the fuel pressure and exhaust back pressure. Which I have no gauges for currently.

Sorry for the long post. I just wanted to be as thorough as I could.
Thanks in advance to anyone that may have a suggestion.

 

I didn't read it as thoroughly as I'd like to, but my knee jerk reaction says you may have a bad ground somewhere. How are your connections to the body/frame?

 

That's also what the guy with the snap on s anner suggested.
So I went back Friday and checked every ground I may have disconnected when replacing the intake. Everything was good. I also checked the body/frame grounds and haven't found a single one loose. I'm sure there may be some I overlooked but checked the obvious ones.

 

Is the torque convertor locking up? It doesn't in 1st, but beyond that it does. If it's slipping you'll lose all kinds of power.

 

So did you actually unhook the grounds and clean them? You could have corrosion underneath causing bad connections.

 

Yep, exactly. Especially if you live in areas prone to more rust.

 

As far as I can tell the trans is shifting just fine. I was getting a transmission range sensor high input CEL but I cleared it and it hasn't come back in several weeks.

I did. I cleaned the hell out of them. I was getting bad corrosion on my negative battery post so I cleaned every ground I could find.

Luckily, south Georgia isnt very rust prone 😂

 

Which would be the main grounds I need to check incase I missed one?

 

Across the firewall from the right, - Cab grounds , - PCM direct ground, battery ground and finally, -intake/engine ground. They all ground to the cab. Another cab ground that is the first to disintegrate is the cab to frame ground which is under the pass side floor. That one always goes first as Ford used copper braid. Not only does it take road rash but nekkid copper will corrode quickly in braid without protection.

Headlight/horn grounds also rust up, they are at the top of the core support...radiator support.

Check the cab grounds inside behind both kickpanels, - note: drivers side has two.

Main battery grounds are next to starter and on the frame rail by pass side tire. They are Engine and Frame grounds.

Absolute ground is not the alternator unless the connection between alternator and block matting surfaces are clean with good contact.

 

There's no harm in checking grounds but why would a ground be fine when cold or in first gear and get lost in second and be found again by feathering the engine? Just my 2 cents but I doubt you have a ground problem.

If it's the torque convertor the transmission can still shift fine. It's just not locking up. It's like a slipping clutch that finally grabs.