Ok so yesterday I was on my way home from Las Vegas, about 50 miles outside of Barstow. I had cruise control set at 85mph. Then the truck started shaking, I lost power and check engine light started flashing. I pulled over about 1.5 miles later at the next exit. Checked wiring, nothing seems wrong. Test drive it for a little bit. Seems good idles fine. Get back on the freeway and less than 5 miles later same story. I was able to limp to Barstow in the slow lane. It didn't like going up hills. Bought a obd scanner in Barstow, got 2 codes PO301 and PO303. I replaced cylinder 1 and 3 coils. Test drive on the freeway. Same issue pull off freeway, same codes. Replaced the cylinder 1 spark plug (just to troubleshoot) test drive, same issue, pull off the freeway now only 1 code PO301. Ended up getting towed 85 miles home. I noticed a faint rattling when it would lose power at high speed or going uphill. Want some advise on where to go forward. I'm thinking fuel injector cleaner, but I don't trust it that much. Almost rather replace them. I'm not sure where to go. Anybody experience this?

 

Check your FPDM for corrosion and integrity.
It's located above the spare tire. Lower the tire and take a look.
The FPDM controls the fuel pump output.

Other possibilities:

Worn out spark plugs, ignition wires, coil(s)
Vacuum leak(s)
Low or weak fuel pressure
Improperly functioning EGR system
Defective Mass Air Flow Sensor
Defective Crankshaft and/or Camshaft Sensor
Defective Throttle Position Sensor
Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems
Common Misdiagnoses

Fuel Injectors
Oxygen Sensor(s)

 

Alright so I visually checked the FPDM, no trouble found. Contacts looked good, wiring looked normal. I checked the 5, 6, 7, and 8 spark plugs, wires and coils. All normal. Should I check something else or replace the FPDM for good measure? I test drove it again after I was done and once again no problem until I got to high speed (80-85mph), drives around streets fine no issue, no trouble idling.

 

My 08 is doing the same thing, the #3 cylinder misfires at 55mph and its been at the dealers for almost 2 weeks, for the 2nd time. Its only got just over 50.000 miles. I just bought the truck, and in 2 days It will fall under the lemon law. Am I looking at a future of head aches or is this a very fixable problem ? because I really liked the truck. HELP
Thanks Jay