Engine cuts out/partial power, then comes back- here's what I've tried so far.

Alright- I need some help here.

2004- 350k miles. The big problem- the engine drops to partial power intermittently for about 2-5 seconds when driving, but it seems to recover if I pedal to the floor. then drives normal for a while, then does it again. I've been driving it cross country like this with a trailer, so it runs well enough to go on the highway long distance, but it sure is irritating. Additionally (and I asked about this in an earlier thread but got no real responses) #3 cylinder misfires when cold, likely from a weak ring that is blowing some oil. Clears up after about 30 seconds of running. This is a problem, but its less of a problem than the whole engine going partial power intermittently. That's what I'm trying to fix for now.

What I've replaced within the last 5k miles trying to find the problem:
New in tank fuel pump and filters
New frame fuel filter
All new injectors
All new coils
All new spark plugs
All new coil wires

What I suspect might be the problem: there seems more and more to be a link to the throttle position. I don't have the best understanding of what sends the firing signal to the coils- is it possible a bad TPS or MAP sensor could be causing the loss of power? These aren't the cheapest replacements (neither were the injectors) is there a way to test them?

Thanks for any technical help.

 

Things like this are super hard to isolate.

I've recently replaced a 3.4 ECU at work, and they are bullet proof.

The misfire when cold is likely a slow leaking headgasket, they mist coolant overnight, its so small you don't see the level change, but its enough to cause a cold miss.

With this intermittent power loss, I'd be personally leaning towards the ignitor or a relay. I tend to swap relays around from high use, like EFI to a low use like wipers etc if they are compatible.

Throttle position is possible, but if its the electric throttle model it would typically throw a code.

 

I’ll guess igniter, too.

 

Igniter- thanks guys, that will be my
Next replacement, next week. Will report back!