F150 Lack of Power Under Load [FIXED]

1999 F150 4.2l 2wd with 311,000 miles. It's my everyday vehicle that I use back and forth to work sites. It was running great up until a couple of months ago when it started to lose power on acceleration under load. It has become increasingly worse in the past weeks. It usually only happens when I run the truck for an extended period of time. My travel times average around 1 1/2 - 2 hrs highway with some start and stop city driving. On inclines I some times cannot get it to go faster than 10-20 mph. I have a second gen Modis scanner that I use for trouble shooting my vehicles. I just want to say I'm not a professional mechanic by no means, more a student. I have Pauls book and have been watching all the videos. I would appreciate any of your knowledgeable input as to what direction to head to trouble shoot this issue. Some of the things that I've done so far are; Replaced plugs, wires and coil (coil was original ), fuel injectors were replaced at 209,000 miles, Fuel pump about a year ago, fuel pressure regulator last week. I've also run a cylinder contribution test, using the Modis, while driving back and forth to work. It consistently showed cylinder #3 and #4 at -14 to -17 when the loss of power occurs. Any help on this would greatly be appreciated.

What do your maf readings look like at idle and at wide open throttle while driving

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Also what does your front 02s say under same conditions as maf test

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If possible I'd like to see these tested when it's acting up but may be able to get something useful out of it even while it's running ok

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Circled area is at WOT. This doesn't always happen. Checking mode $06 Test Id $53 I found cylinder 3 with 218 misfires and cylinder 4 with 436 misfires. Hopes this helps.

Nice capture! Seeing the MAF get to 4V eliminates a lot of potential suspects.

Also, good idea checking Mode $06. On a hunch, I Googled the firing order for this engine:



Cylinder #3 and #4 are companions, and share the same primary circuit in the ignition coil. Its just a guess, but there could be a primary issue going on that's causing weak/no spark to those two cylinders.

#3 cylinder secondary waveform . . . At idle.

Can you scope the primary current for that coil?

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Your title has [FIXED]??
i am lost what was the fix?

Second set of wires for the fix. Originally replaced wires and plugs before I switched out the coil. Seems that somehow the coil burned out a set of wires, cylinders 3 and 4. When tested with an ohm meter both tested open. Found this intermittent fault while moving the wires while scoping the secondary on 3 and 4.