I won't go into the full detail my previous posts will explain my overheating trials. I finally resolved the overheating after replacing the Radiator. My CEL is showing P0307 which is a cylinder 7 misfire.
Truth be told I believe I had a small head gasket leak and used the cursed Blue Devil which seems to have solved the leak. I say that because the head gasket leak detector fluid had a slight change but
nothing dramatic there were not other signs of a head gasket blown except the fluid and the code P0307. Now the fluid stays blue no change at all. NOW my question when I drive the truck it idles a little
rough and when I am at highway speed around 2000 RPM and when at constant speed the truck starts to vibrate resembling a tire out of balance ANY change in the throttle will stop the vibration until
the same situation resurfaces ie 2k rpm or steady speed. I do have the CEL light and at times when the vibration starts the CEL will flash then return to steady.

Anyone have any idea what may be causing this could it be plugs or wires?
What is the difference with a CEL flashing and steady
And lastly will I do any damage driving the truck with the vibration.
I know the easy answer is the head gasket but with that answer I need to know why doesn't any other signs show up like exhaust smoke/steam, blue fluid color change, water in oil, or coolant puking out radiator?
I am running out of hair to pull out and money changing things that don't need to be changed my next step is new wires and if I can get the plug out check the Cylinder 7 plug

Sorry so long but I appreciate any help

 

iirc CEL usually flashes for a misfire detected

now just thinking out loud, you may have checked this stuff already idk.


headgasket can go one of 3 ways

1) cylinder to coolant jacket
2) cylinder to oil passage
3) oil to coolant

have you checked your oil level? is it dropping faster than normal?
it sounds like the cylinder to coolant jacket is fine if your not getting exhaust in your coolant and your not loosing coolant
what does your oil/coolant look like? are they both clean?

my best guess is that the vibration is caused by the misfire your getting, you tell me if you think its a good idea to drive a truck with that serious a misfire going on . . .

 

The same thing happened to me last week. Driving home from work, sudden vibration, lose of power, flashing engine light for about 10 seconds then solid engine light. Drove straight to the dealer (its on the way home anyways). They scanned and found misfire on cyclinder 7, turned out to be the coilpack. Changed out and all good. 2011 1500 Sport Crew

 

I've checked the coil pack switched it with #1 and code didn't change. Have done the night time spray bottle check and have seen a few sparks from wires but none from #7that I can see since it's in the back.
Te oil/coolant looks clean it is due for an oil change but no discoloring in the oil due to changing the radiator, water pump, fan clutch the coolant is brand new. Oil level is within normal not even a qt low so not dropping that I can tell. I have done the block test with the blue fluid and it came back no change. but like I said when I initially had the overheating issue I tested it and it did change but I literally had to take a pic with my phone of the before and after just to see if there was a change I showed it to a couple of mechanics and one said oh yeah that's a change the other said nope looks good to me.