Misfire cylinder #6

[Mopo47]

I have a flashing check engine light that comes on when accelerating. The code that set is 0306. The truck seems to run ok, no severe shaking or chugging. First thing I did was replace spark plugs. It definitely needed this. No change. fuel pressure test- 60psi. Swapped coil with another cylinder, swapped injector with different cylinder, compression test- 150psi. No change. Full disclosure, I didnt pull a plug from each cylinder or have wot when I did the compression test. I just pulled the valve cover to inspect the valve springs because I have read a few things about that. Dont see anything obvious just looking. The engine does seem to have a little sludge buildup. What should I be looking at valve train related? I realize I should probably circle back toward wiring I guess. I did inspect the wire harness, and unplugged #6 coil while running and it created an obvious miss. I'll also add that with scan tool hooked up for road test it showed the misfires racking up when accelerating and I looked at the cat temp, the highest it got was 1,600* if that matters. Any help is greatly appreciated! I'm a little short on time these days and it feels like I just wasted an afternoon!

 

[Tim Garceau]

When you had the valve cover removed, did you crank it over and check rocker travel?

Sorry in advance.

 

[Mopo47]

I was trying to turn it over with a ratchet, it looked like everything was moving fine. Os there a more scientific way to measure this?

 

[Tim Garceau]

Not sure if the 3rd Gens cut ignition with the pedal to the metal.

 

[Mopo47]

Well I just found a helper to crank it over while I watched the valves. It is pretty apparent that the intake valve on #6 is not traveling as far as the others

 

[OCDTech]

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[Karlsweg]

Bent pushrod?

 

[Redtruck-VA]

Don't know why, but #6 is often the culprit with a broken valve. Wiped lobe not often. My money is it will be the spring.

 

[Mopo47]

Well I guess I could pull the rocker shaft of and check the pushrod. The valve appears to come up and seat, which is why I have compression. It looks to only push down (open) about half the distance of the others. Truck really doesnt run bad. A little lower on power maybe but doesnt have a bad miss. I was kinda figuring collapsed lifter or worn cam.

 

[Bloody_Knuckles]

There is another post here that says that for some reason broken valves on the 6 cylinder is more likely than other cylinders.

 

[LoneWolf3574]

Well I guess I could pull the rocker shaft of and check the pushrod. The valve appears to come up and seat, which is why I have compression. It looks to only push down (open) about half the distance of the others. Truck really doesnt run bad. A little lower on power maybe but doesnt have a bad miss. I was kinda figuring collapsed lifter or worn cam.

Maybe the lifter isn't pumping up fully or possibly a wipe cam lobe?

 

[Mopo47]

Maybe the lifter isn't pumping up fully or possibly a wipe cam lobe?

This is what I'm thinking. Unfortunately I wont be able to get back to this for a little bit. If I pull the intake will I be able to get a look at the cam and lifters?

 

[scott lass 18]

I have a flashing check engine light that comes on when accelerating. The code that set is 0306. The truck seems to run ok, no severe shaking or chugging. First thing I did was replace spark plugs. It definitely needed this. No change. fuel pressure test- 60psi. Swapped coil with another cylinder, swapped injector with different cylinder, compression test- 150psi. No change. Full disclosure, I didnt pull a plug from each cylinder or have wot when I did the compression test. I just pulled the valve cover to inspect the valve springs because I have read a few things about that. Dont see anything obvious just looking. The engine does seem to have a little sludge buildup. What should I be looking at valve train related? I realize I should probably circle back toward wiring I guess. I did inspect the wire harness, and unplugged #6 coil while running and it created an obvious miss. I'll also add that with scan tool hooked up for road test it showed the misfires racking up when accelerating and I looked at the cat temp, the highest it got was 1,600* if that matters. Any help is greatly appreciated! I'm a little short on time these days and it feels like I just wasted an afternoon!

ya mine was on 1 but fuel injector it sounded like the others but was bad hummm then exhaust leek replace on one side bolts broken steering fix trans mod redone runs great but axle now going it to be check by pro s hearing lifters going out scares me hope mine are ok ! amsoil every 2,000 ! need truck 4 more years ! better to replace engine if this is it ok !

 

[scott lass 18]

This is what I'm thinking. Unfortunately I wont be able to get back to this for a little bit. If I pull the intake will I be able to get a look at the cam and lifters?

no cant see cam so sucks right a big job heads off to see