Chasing Misfire

[badandyturbo]

Hello friends. I have been hunting down a misfire in cylinder 2 for a bit now and I need some help.

Code is P0302. Misfire cylinder 2
I have swapped coilpacks.
I have swapped plug wires.
I have replaced the spark plug.
I have replaced the injector.
I have pulled the valve cover and checked rockers.
I have used 87 octane and E85.

Truck misfire is only noticeable at temp on idle. Cold start and driving it's fine.

Any other ideas?

 

[avalonandl]

Head gasket or intake gasket is my "guess"

 

[donjetman]

Somebody here recently finally cured their misfire problem by replacing either the coil pack wire harness. See post# 36 in the following thread: https://www.tahoeyukonforum.com/threads/persistent-misfire-cylinder-3.115593/page-4

 

[OR VietVet]

What is the compression on that cylinder compared to the others?

 

[Doubeleive]

Like Ron said compression test and I would check the injector harness voltage, check all 4 connectors on that side and see if they all read the same, it's not uncommon to have a bad harness.

 

[OR VietVet]

Yea, if you have a compression problem, that simple basic test could have saved you all this time chasing the problem and any parts you threw at it.

 

[badandyturbo]

Thanks for the advice. I will do the compression test first.

 

[OR VietVet]

If you do that compression test be ready to do a dry and wet test. If the compression is low, compared to other cylinders, then remove that tester and spit a little oil in that cylinder to see if the compression comes up. If it does, then rings are suspect, if not, then valves or head gasket is likely.

 

[badandyturbo]

Ok so the compression is good. I have also used a noid light to check the injector. Its firing correctly. I am running out of options......

 

[Doubeleive]

maybe hook up a scanner and get a live data feed going and try wiggling the injector wire harness and see if it correlates with that. If the hardware is good then it must be electrical.