F150, Auto, 4x4, 4.6, 2 coil packs
Have 3 cylinders that work, 5 cylinders that appear to be "dead". I did a balance test by unplugging fuel injectors and cylinders 1,2,and 3 were working. Cylinders 4-8 appeared to be "dead". Ran a compression test on 4-8 and they were all within 120-150lbs. any ideas?

 

I sense there may be more to this story.
What are the codes so we are not missing something.
As of this moment you have 5 cylinders out and no cause to point to.
Good luck.

 

Ok so here is an update. The motor had a massive oil leak at the front seal. We decided to yank the front cover to fix the seal and check base timing. After marking the chains we found timing was dead on but the chain were stretched. They had expanded so much that the tensioners could not adjust anymore. After ordering two new chains, inspecting the guides/tensioners, and timing the engine per the FORD WORKSHOP MANUAL we re-installed the front cover and valve covers. We also threw in 8 factory-spec plugs, a new fuel filter, and cleaned each injector with carb cleaner (I know that probably was a waste of time but who cares?). We crank it, and it fires right up, no misses, hitting on every cylinder. It is so smooth we could balance a quarter on edge. Then we went to drive it. Under very light load, everything seems ok. But under more than quarter throttle at load, it misses and spits and raises hell. We were able to get it up to highway speed pretty easily but misses while accelerating. We do have one cylinder that is at 90 psi compression but if it was a compression miss it should show up every time the cylinder fires, not at random like it is now. It almost doesn't feel like a miss either, it feels like there is a switch going on and off adding and subtracting about 20hp? any ideas?

 

btw fuel pressure within spec, tested with a gauge.

 

I feel your a point that a Scanner needs to be used to look at mode 6 test 53 to look at the misfire monitors for each cylinder looking for any cylinder that has high counts and go after the cause.
Without it's just guessing and luck plus cost replacing part in a hopes.
A 90 psi cylinder should fall out of the 10% rule on compression.
It may or may not set code for that cylinder.
You already did well so keep at it because the motor apparently has a lot of wear.
Good luck.

 

thanks for the encouragement! I bought this as a cheap fixer upper so ive been trying to avoid the "replace random parts" method. The motor has got to have atleast 200K on it, but no real way for me to tell as the odo is busto. Ill update as I progress.

 

The motor has coil packs so be sure the plug wires are in their correct sockets and inspect those sockets for flashover problems.
Good luck.

 

So here is an update, this is the best I have gotten it to run so far.

 

What are the Check Engine light codes?

 

P0401, egr code because I broke the sensor and haven't plugged it back up

 

quick question on the side. Anybody know a good machine shop around the Richmond, Va OR Augusta, Ga area? I know they are rather far apart...don't ask

 

So finally figured out what was ailing the truck in the 11th hour. I put it all back together to get it ready to sell, took it for another test drive, and got a check engine code. I decided to check it just for the hell of it, and it was a cyl 3 misfire. Took out the wire and sure enough, it's bad. Decided to go all in and replace all the wires. Thing runs like a champ. It seems a little sluggish to me but it does have 250K+ miles on it. No misses at idle, no misses during acceleration, no misses in O/D. Truck still needs work, but the big issue is now fixed.

 

Good you found it. That's the problem with check engine lights; if you leave a code unaddressed you can't tell if a new one has popped up unless you keep checking for codes periodically or notice the engine runs differently.