Whats good:
- truck idles great, no misses at any speed
- pulls very hard, will smoke the drag radials with a quick mat of the pedal, shifts hard enough to snap your neck
- no codes on autotap

Whats bad:
- will only go 100-110mph... max. Feels like hitting the rev limiter at that speed, it just will not go faster. Start feeling it stumble once it gets over 90mph

Has new plugs, new chip (did it with old/no chip as well), injectors all flowing fine.

Sooo... what the hell is the problem? Fuel pumps? Coil packs? I need a hand figuring this one out.

 

Ever change the fuel filter?

 

Yep, new motorcraft filter just this week.

 

Maybee the vehical speed sensor, I don't know it is just a guess

 

I think Vinnie had a simular problem and it was his coil packs but dont quote me on that!!

 

Vinnie did have similiar problem, the truck was dying on the top end.

Turned out to be 2 bad coilpacks.

 

If engine lacks power:

1. Incorrect ignition timing(not likely?)
2. Faulty or incorrectly gapped plugs.
3. Dirty air filter.
4. Faulty ignition coils.
5. Brakes binding.
6. Auto. trans fluid level incorrect causing slippage.
6. Fuel filter clogged(you changed it).
7. EGR system not functioning properly.
8. Use of substandard fuel.
9. Vacuum leak
10. Dirty fuel injectors.
11. Restricted exhaust.

?????

Dan

 

We are just shooting in the dark without knowing what your mods are son. Give us some info to work with. If I had to guess your running a chip of some sort and its leaning out and starving the engine for fuel. I've seen it before. If Im correct on this you are real close to breaking a rod or burning a piston at this point. Can you hear any ticking in the engine with the windows up and the radio off? Real fast clicks not clatters. Tell us your list of mods and what kind of plugs you put in. ETC

 

Could be Throttle-Body related if you have an aftermarket.

 

Its not a chip issue, as I said I tried it with the old Superchip, with no chip, and with the current Diablo chip. Same results.

Currently I have a 5# pulley, ported upper with intake tube and K&N filter, and thats about it for the motor. FT valve body is the only other drivetrain mod. Looking at the three gas reading from this past Saturday's dyno run at REM, the motor is running fine with the fuel curve. The plugs are NGK R-5724-8's, basically their race -8 cold plugs. Had similiar symptoms with Denso IT22s, other than a miss due to two broken plugs, hence the replacement of both plugs and chip. Exhaust is stock.

 

Hey Hooters my Pal, how you been man

2Cool I remember your post some days back saying you saw the problem on the Dyno and switched the highest flowing injectors to the two cylinders that had the bad plugs. You didn't mention it was totally dieing at top end, that sounds like fuel delivery to me. It also seems the problem that made your Denso's go bad is still there. There was nothing wrong with the Denso's, there's something else wrong.
LISTEN TO WHAT HOOTERS IS TELLING YOU
They run strong when they're lean, BUT DANGEROUS
All it takes to go from this

TO THIS

Is 60ft into a 1/4 mile run.
They run strong when lean, and even you said the other day a couple of plugs looked lean.

THE POINT IS YOU GOT A SERIOUS PROBLEM THAT NEEDS TO BE FOUND AND FIXED RIGHT NOW BEFORE YOUR MOTOR GOES BOOM


My Guess is you may have the Fuel Pump problem L's are famous for ""if it's not a coil or two"".

 

DO the miraculous radiator flush. Better then your colon!

 

ttt one time

And I did mention that there was still a problem, and that I needed to run a load balance test to determine if there was a problem with the coils. I took it in for that, but the head mechanic at our local dealer tells me that the coil packs don't go bad (?) and that the only part that is a problem sometimes is the boot, which is easily replaced. Being as I hadn't yanked all of my mods off the truck, and he was good enough to overlook those, I couldn't push the issue too much.

So right now I am looking at either a new fuel pump setup, or buying some coil packs and doing some trial and error swapping. Likely also put in a boost and fuel pressure guage pod as well, so I can see if the fuel is falling off under load.

 

He's wrong(misinformed?) about the coil packs. Several(many?) guys have found the #3 and/or #4 coil pack have gone 'bad' due to coolant leakage from lines running above them.

Never heard of a 'boot' problem? All it does is hold the contact spring between the coil bottom and the plug top and it insulates the plug.

Dan