Hard idle at cold start up - 1998 B4000

[aroundincircles]

I've been around the block a while and done a lot of work on my 1998, some of it has even been posted here.

But I've run into a new problem that has been on-going for a while, and I'm not sure what direction to go, and I've taken it to two shops who both gave me very different diagnosis and were unable to resolve the issue. Namely I've had a very hard/rough idle at start up, and that has progressed to a stumbling idle once warm.
One shop told me it was an intake plenum gasket leak, so the replaced that, and it didn't fix the issue. Another one told me that it was a blown head gasket, but I am experiencing no loss of coolant, or water/oil mix. I will be doing a compression test, but my tester didn't have the right size adapter, so I'm waiting on that to show up.

Here are the spark plugs:

And here is a video of the individual cylinders:

any suggestions on where to look would be appreciated. I'm completely at a loss as to where to go from here.
I was in the middle of the move when I took it to those shops and I now live hours away in the middle of no where, so taking it back to them isn't an option and I don't know what shops to trust in my new area.

 

[PetroleumJunkie412]

Hard idle creates strong engines
Strong engines create autotopia
Autotopia creates low output
Low output creates hard idle

Or something like that.

Idk I'm not a mechanic.

 

[sgtsandman]

Some of those plug threads look pretty groady. So, there could be a valve cover leak dripping down on them. Anyway, I believe the spark plugs ground through the threads into the block. All that crud could be causing a lot of resistance and thus the rough idle.

 

[4.0blue98]

Was it just me or does cylinder #6 look oily and unlike the others? Plugs do look strange. Compression and leak down tests would help. Should get a code if it's misfiring on a particular cylinder, but ever pull a plug wire while idling weird and see if it changes?

 

[aroundincircles]

Got the compression test done:
3: 150 6: 130
2: 130 4: 118
1: 145 4: 130

So driver's side is a bit lower than passenger, but it's not super out of spec is it? that 118 has me worried. I also saw this on injector one:

 

[sgtsandman]

Was it just me or does cylinder #6 look oily and unlike the others? Plugs do look strange. Compression and leak down tests would help. Should get a code if it's misfiring on a particular cylinder, but ever pull a plug wire while idling weird and see if it changes?

It looked oily to me as well.

 

[sgtsandman]

Got the compression test done:
3: 150 6: 130
2: 130 4: 118
1: 145 4: 130

So driver's side is a bit lower than passenger, but it's not super out of spec is it? that 118 has me worried. I also saw this on injector one:

It looks like it’s missing a wire. That would cause an idle issue if that is indeed the case since the injector wouldn’t be spraying fuel. That wouldn’t happen to be #6 would it? That would explain way the piston is oily.

 

[aroundincircles]

It looks like it’s missing a wire. That would cause an idle issue if that is indeed the case since the injector wouldn’t be spraying fuel. That wouldn’t happen to be #6 would it? That would explain way the piston is oily.

No, the red wire goes to something else, the white thing is the injector and it has both wires and has that white junk around it. Not sure what that is. This is cyl 1.

what causes a piston to be oily?

 

[sgtsandman]

The oil could be from a leaky valve guide or a head gasket leak. #6 spark plug looks like it has some oil fouling on it as well.