Misfire on cylinder 4 misfire help please.

[gmfan454]

Any help would be appreciated. My nephew has a 96 C1500 with the 5.7 and was getting a random cylinder misfire code. We changed the plugs to platinum (forget brand but wasnt Delco), the distributor cap and rotor, both 02 sensors and now it is giving the cylinder 4 misfire only. Any idea what it could be?

 

[michael hurd]

It could be that plug wire or possibly a broken rocker arm on that cylinder. A compression test would help you out in diagnosis.

 

[skylark]

As above, compression check. Swap that plug wire to another cylinder and see if the problem moves. Bad injector. Leaking intake gasket.

 

[Rusty Nail]

Cracked spark plug insulator maybe? Move the coil to a different cylinder and see if the misfire follows.

 

[twomanymontes]

Seeing as it went from a random misfire to a solid Cylinder #4 misfire, I would check that spark plug 1st. Swap it with another cylinder and see if the misfire changes to that cylinder. It wouldn't be the first time I have gotten a bad plug out of the box. Might want to run some seafoam though it as well.

 

[michael hurd]

Cracked spark plug insulator maybe? Move the coil to a different cylinder and see if the misfire follows.

You mean move the plug? Vortecs only have one coil.

 

[Rusty Nail]

lol....yeah they do! Thanks dude.