I do not believe that a 5.4 will idle on three cylinders. In more specific terms, I do not believe that you could disconnect the 5 coils that made no difference, all at the same time, and still have the truck idle.
I do believe that disconnecting them one at a time made no apparent difference.
Conclusion is that 3 cylinders are strong, 5 are weak. Since you didn't bother to enumerate the strong and weak cylinders, I have one wild guess:
One bank, 4 cylinders, is messed up, either the cam is off or the fuel rail or some other component is malfunctioning. One cylinder on the other bank has a bad cop or injector.
If you do shoot the truck, please specify which cylinder and caliber.
Then it appears that cylinders 1 and 2 are working normally on bank one, and cylinder 7 on bank two. If that is the absolute truth, then I would rule out the cam timing and phasers.
A compression check would be my next step. I would also repeat the coil disconnects and double check that you get the same results for the same cylinders. I would also place a new plug on the disconnected cop to make sure it is a good, hot, blue spark.
Just had a thought... I removed the timing chain cover when I did the chains, and as a result removed the crank trigger... it went back on as it came off, with the "fingers" facing forward (towards harmonic).
Maybe 2 thoughts-
1- I wiped off the crank sensor with a rag as it had some metal on it from where previous chain debris on it...bad ??
2- reused harmonic bolt... learned after that OF COURSE its F'N TTY. I am about to run out and look... I wonder if that sucker is about to give?
UPDATE: Harmonic is not wobbling whatsoever.
95 GMC Suburban 2500 6.5 turbo diesel, 93 Mustang LX 5.0, 87 Jeep Grand Wagoneer 360 v8, and a nifty 2005 F250 SD with a 5.4 3v...
Last edited by Steve93mustang; 06-01-2011 at 11:35 AM.
Wiring IMO Check the harness. Check PDB fuses. Your intermittently losing power to all 8. Something was bumped or damaged (wiring). Make sure the harness has not contacted the AC accumulator or very close to. If so, tie back. The mag field can create ignition havoc. Specially if any of the wires loose their foil insulation.
It has to be intermittent. Otherwise the engine wouldn't run, via 351-358.
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