I have an 07 with a 5.4 with 162k miles ,that Otherwise runs like a champ. Ive taken great care of this truck as far as maintenance , OiL changes , Plugs Coil Boots, But i noticed a hard mis or stumble =during hwy condition at 65PMH or higher. while Truck is in OD and if accelerator is slightly pressed the motor misses and stumbles, if it down shifts and the pms's go up, runs fine. I had this before and replaced all the coil boots and plugs and it went away, but I put around 20k miles since they were done and its back again ??

 

Test your fuel pressure.

 

look at mode six to see which cly are involved . its under test results on torque pro same as a mode six goes down each cyl and displays raw computer counts towards a misfire. Try it on a hill in high gear .Could have a bad plug or carbon build up ,its nice to clean spark tip area out in cly with carb cleaner . Also scape and clean all cop terminals . Make sure no oil or anti freeze in there ruining boots . You should be running sp546 plugs but that carbon can break new plugs going in .go easy on dielectric grease a little on each end of boot . use contact cleaner on connections . I like to change injectors after 100k miles . clean those connectors also . check that all cop and injector connectors lock on if not solder new pigtails in .do not twist connect anything- corrosion and vibration not good for twist type stuff .do not use those blue piercing uhaul types either.

 

You're feeling the miss because the converter is locked up on the freeway. Were the coils/plugs OEM parts? I've seen a ton of repeat failures with cheaper stuff.

 

All symptoms of plugs or COPS failing. Pull them and look for cracked insulators and carbon trails.

 

What am I missing..."Mode Six " I've been working on,in and around cars and trucks my whole life, never heard that expression LoL..

 

ALL Coils, Coil Boots replaced withing last month (Standard Ignition Coil) I know----I know OEM Coils Only....I did some research, these aren't as bad as Most other after market coils... Plugs have about 40 k on them, But maybe now one or two plugs is loaded with carbon ??

 

Mode six is an obd 2OBD II Mode 6 is unfamiliar territory for many technicians. Valuable (but occasionally cryptic) diagnostic information can be found there, if you know how to look for it.
Mode 6? What's Mode 6? OBD II is divided into modes as defined by the EPA and SAE. These modes and their operations are defined in SAE On-Board Diagnostics for Light and Medium Duty Vehicles Standards Manual. This manual can be purchased from the Service Technicians Society (STS) at their website, www.sae.sts.org.

OBD II modes are:

*Mode 1: Real-time data, MIL, IM monitors.

*Mode 2: Freeze frame.

*Mode 3: Stored DTCs.

*Mode 4: Clear/Reset DTCs and emissions-related diagnostic information.

*Mode 5: O2 monitoring tests, supported.

*Mode 6: Test results for continuously and noncontinuously monitored systems, supported.

*Mode 7: Pending DTCs.

*Mode 8: Request control of on-board-system, test or component (bidirectional controls).

*Mode 9: Request VIN and other data.
Mode six is under test results on torque pro. Its a 5$ app using a android phone/cheap bluetooth amazon reader .

It basically gives raw computer counts by cly towards setting a code. It lets you know where the trouble is cly wise . It also tells you the max number at which it will set a code.
Failure to torque plugs in 25-28 foot pounds causes loose plugs . The sp 515 plugs went bad right out of the box . Non oem cops are not good . oem cops should have their terminals cleaned as they do .corrode. Don't over do dielectric grease and do a hospital clean install . If you use antisieze be very careful . I only use a very small amount .
Fluids in sparkhole ruin boots as well as blowby from loose plugs .
I changed all my injectors by this mileage , I do think they get overworked.
All this should help you zero in these classic misfire symptoms , Mode six counts can be held to zero if done right.