I’ve been trying to figure out a misfire and I’m putting my rocker shafts back on. All of the lifters, rods and rocker arms are tight on one cylinder bank as I expected. Most of them are loose on the other side after installing. There seems to be some play in the lifters allowing the rockers arms to move some. Is this normal? I’m assuming they will pump back up with oil and take up the slack once I start the engine?

 

I believe your assumption is right, they are hydraulic.

Pretty extreme digging for a misfire.

You ruled out all the usual suspects first?

Try a leak down on the misfiring cylinder, could be a blown head gasket between cylinders.

 

At least 3 shoudl be tight due to the valve timing (valve open). If one is on the compression stroke then it could be slightly loose. The other three cylinders should have at least one valve open, the other one could be slightly loose.

How many cylinders are misfiring? All on that side? Unlikely but possible you have a worn rocker shaft or worn out cam? Did you check the lube feed hole to make sure it was open?

 

Yeah I got myself into this deeper than I wanted. My misfire was getting worse over the last few months or so. P0306 thrown a lot with P1319 thrown only once.

So far I replaced spark plug wires (seemed to help for a little while),
swapped plugs with another cylinder,
new crankshaft sensor
new muffler that was long overdue along with fixing a leak at the manifold/pipe.

Did a leak down test with my cheap harbor freight tester that gave results all over the place. While my new Leakdown tester was being shipped I decided to pull the intake to switch the coils around and swap injectors. My new Leakdown tester arrived so I just pulled the rockers arms off so all the valves would be closed and I could test it. All cylinders were around 10% leak give or take a few.

I had to pull the lower intake because a lifter came out when I took the rockers off. Lots of carbon buildup noted on the intake ports and the valves were leaking some as air was bubbling up through the little bit of coolant that got in there. I guess that was minimal though according to the leak test. Interestingly cylinder 8 intake was a lot cleaner than the rest. Maybe there was an intake leak there or something I don’t know.

Now I’m putting it back together, if the misfire doesn’t move to another cylinder I’ll do a compression test. Any other ideas are appreciated. I just thought it was very odd all of the lifters were tight on the drivers side, nothing moved there. The passenger side did have 3 or 4 very tight, the rest had some play in the lifters. I just want to make sure that’s okay since coincidentally that is the side with the misfire.

oh yeah, the heads were rebuilt about 20k miles ago

 

are you talking about the holes coming up through the head to the rocker arm pedestals. Or something in the rocker arm? No I didn’t

 

the whole the whole feeding a pedestal was exactly what I was talking about. How many miles on the truck since it had head gaskets? You got all the way down to the lower intake and the Rockers off, the only thing between you and a head gasket job was the exhaust manifold bolts and the head bolts, I never take them down as far as you've gotten yours without replacing the head gaskets if I know they haven't been done in quite a while. That would also give you a look inside cylinder number 6 and at the head gasket tell if that's the cause of a misfire.

It's highly unlikely but if you had a worn camshaft, rocker arm, rocker shaft it is conceivable that would be the cause of you're misfire.

What have you put back together so far?

 

Headgaskets were done maybe a little less than 20 k miles ago. Yeah it’s tempting to pull them off but I’ve done them twice already and I don’t want to get into the time and money involved with that if I don’t have to. The first time I replaced them because I was just doing the lower intake and decided what the hell I’ll do the heads too since I’m there. I should have just left them, of course back then I only had a intake leak and I didn’t have the heads planed so they started leaking again later on.

 

Did you look to see if the lifters had any dish on the surface where the cam lobe rides? I had a good bit of dish on 3 of mine and slight dish on most of the others. Swapped them out and actually the truck has more pep. I dont believe it would be enough to cause a misfire but ya never know.

 

A lifter came out ? When I took my rockers off, I then removed the push rods. The lifters stayed in place. Was a push rod stuck to the rocker and lifter?

 

No I didn’t look closely at the lifters unfortunately but I didn’t notice it on the one that fell out ( happened to be my misfire cylinder) My engine rebuilder said the lifter wouldn’t cause a misfire though