hope95

I have a 2004 ford f150 5.4 triton and there was something wrong with the timing chain so bought a new one and also new, coil packs, spark plugs, rockers, lifters and cam shaft. We did all of that because when idling the truck would misfire horribly to where the whole truck felt like it was just going fall apart. That stopped and now when you get up to 40mph and just cruise the rpm will shoot down and start to stutter and not move and you'll either need to let go of the gas and hit the break then hit gas again or let go of the gas and hit it harder and it will go up again and the truck will speed up. Because when the rpm drops and doesn't move it loses speed. It does this any speed over 40mph. I thought it could be coils but they are all brand new including spark plugs. I've been told it could possibly be the timing chain and it could even be one tooth off but it does misfire badly like it use too. Cylinders 1 2 3 4 misfire while idling but not while driving. Totally lost on what to do and I'm becoming scared to drive it even though it is my only vehicle. It seems to be getting worse, doesn't have a nice pick up unless you floor it and I know it's a big truck but it has a big enough for that reason. It seems a little sluggish. Any help would be greatly appreciated! Thank you!

bubbabud

Intake manifold gasket, EGR valve or other vacuum leak. Possibly bad brake booster.