Gents,
This one has me up the stream....
In a previous thread I mentioned I had the head gaskets replaced 10 months ago and things just weren't right - poor gas mileage and over the course of a few months high oil consumption.
Eventually I had misfires in #1 & #8. Techs at my LR dealership pulled the heads and the valve seals had hardened with oil leaking into #1 &#8.
Replaced seals, installed new plugs, coil packs and my 8mm wires - back in business right?

Engine was still running a little rough and sending a misfir code in cyl#1 - replaced the #1 ignition lead and she idled/drove perfect - dead flat for about 3 miles then the engine light came back on with guess what???
Misfire #1 cylinder...... FML...

To recap:
Headgaskets changed (again), new lifters, spark plugs, coil packs and new(ish 8mm leads) and 1 brand new lead on the offending cylinder.
All I can do now is swap #1 plug with another cylinder and see if the problem moves other than that I am out of ideas - and so are my techs.....
Any ideas would be welcome.

 

How about a bad injector? try swapping #1 injector to the other bank...
If not injector than compression test, and cylinder leakage test recommended..

 

This^
They should have checked that.

 

We did a leak-down test and it was like new...
The fact that the "stumble" went away with the new plug wire is keeping me on the electrical side rather than injector......
I'll add it to the list of other things to try.
This list keeps growing....

 

If everything is good mechanically, and the injectors are good, it sounds like a bad ground.
Check and clean all the engine bay and undercarrige connections.
Something could be loose and/or corroded.
Never fails, something stupid...but they're usually free fixes when you finally find them.

 

What was the condition of the plug? Oil fouled? Wet?

I'm thinking maybe the intake? Did you have the heads done when you did the head gaskets?

 

I pulled the plug and its clean/unfowled.
I had the heads done when they were out -

 

What condition is your rocker shaft in? I know I had a horrible misfire issue after my HG job I ultimately narrowed down to the rocker shaft assembly. After that possibly a very worn cam lobe?

Just throwing some ideas out there.

 

Rocker shafts were tight and in good condition but this is the 2nd head gasket job i've done since buying the truck.
I have 155,000kms on the truck (93200 miles)

What did you do with the assembly - replace it?

 

Come to think of it the misfire occurred 10 months after the head gasket was replaced....
I swapped the spark plug out this morning and it ran great for about a half hour and then upon restarting and driving it misfired again causing the Flashing check engine light came on - code reader says:
- Emission relevant misfire multiple cylinders
- Emission Relevant Misfire cyl 1
It idles a little rough but when I replace the sprak plug it smooths out beautifuly until the next misfire..... AARGH!!!