How many miles on the motor and have the heads been off before?

 

The motor has 139k on it. The heads have only been off when I swapped in the camshaft and lifters. That was at about 98k miles. The only thing I've done since then, is install the new torque converter and trans cooler.

 

I've come across this misfire problem before at work. Ended up being a burnt valve. Passed all the compression and leak down tests but when engine is operating it would misfire. Odd I know, but the valve was pitted including the seat in the head. Valve springs were also weak.

 

I pretty sure I have finally figured it out. To make a long story short, I had someone helping me work on diagnosing the truck who skipped a vital step based on assumptions.

I decided to start over from square one. I pulled all the plugs and started over with a compression test. Every cylinder had 150psi EXCEPT cylinder #1 with 0.
I pulled the valve cover off, and found a broken valve spring on the intake side.

I am going to replace the valve spring today after work. Hopefully this will take care of everything. I'm not sure why cylinders 2 & 4 aren't hitting yet though. Hopefully its sympathy misfires related to cylinder 1. I'll post an update tonight.

Thanks everyone for your help. It has been greatly appreciated.

 

How the hell does someone miss that?

 

Great job on finding it!

It should make more psi in that cylinder now.

 

Agreed!

 

The misfire is just calculation based on how long it takes the motor to get to the next TDC right? So if you had a terrible issue on one cylinder it might throw stuff off so much that the calculation thinks several are bad.

 

Well I had some time at lunch to throw in the new spring. I didn't have time to go drive it, but so far so good. All cylinders seem to be firing now. My truck is finally back to normal.