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P0301 Solved! Lifter failed, but not collapsed. LC9 5.3


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Hey everyone,

 

As someone who scours through forums trying to find answers to car troubles, I would like to make a contribution for a solved P0301 code.

 

I bought this truck knowing it had a miss in cylinder 1, got a good deal because of it. It was a very obvious miss, this truck, while drivable, ran like crap! Immediately started researching everything about misfires on the LC9. First, started with the easy stuff. New plugs and wires, no change. Checked for spark on no. 1 cylinder, it was good. Swapped out the coil pack with the no. 3 cylinder just to be sure, no change. Unplugged the coil pack to no. 1, there was no drop in rpm like there should be with a properly functioning engine. I also made sure to check that I had power going to the coil pack. 

Next, I checked fuel. I could hear the injector "ticking", so it wasn't stuck. I still swapped it out with the no.3 injector, no change. Unplugged the power to the no.1 injector, no drop in rpm. So, onto the next test.

I preformed a compression test, but I learned I can't always trust my tools. It read 90psi, BOOM! I thought I had found an issue as it should read about 175psi. I didn't immediately check any other cylinders, this is where I screwed up. A day or two later, I checked the no.3 cylinder, 90psi... ok maybe blew the head gasket between the no.1 and no.3 cylinders? Checked a cylinder on the other bank, 90 psi...so much for that compression tester...

Then I went to my local Chinese tool store and picked up a new compression tester as well as a leak down tester. Hooked up the leak down tester and nothing... no leaks out the exhaust ( bad exhaust valve/lifter), no leaks out the intake (bad intake valve/lifter), no leaks out the no.3 spark plug hole (blown headgasket), and barely a sound coming out through the dip stick (bad rings). However, I didn't think to check for air coming out through the coolant (blown headgasket). The cylinder actually sealed well enough that the breaker bar I had on the crankshaft bolt spun backwards and almost clocked me in the chin.

At this point I'm thinking blown headgasket or collapsed lifter, even though I don't have proof of either.

I decide to pull the valve cover off and hit the starter. If there is a collapsed lifter, the rocker arm won't move, or move very little. Well, the rocker arms and springs and everything seemed to be functioning just as they should. It looked as though they all had full travel, nothing stood out to me. So that only left one thing, headgasket.

Thinking that I had finally diagnosed the problem, I went to work. I had the cylinder head off the truck in no time, only to find that the headgasket had no obvious fails! I inspected the head for cracks, none to be found. Pulled out the two lifters for no.1, neither were collapsed, I couldn't squeeze them closed by hand, and I know I couldn't pull one of them apart, but I wasn't sure if I tested the other one. I turned one of the rollers all the way around, looked pristine. I GLANCED at the roller at the other lifter and it looked great to!

Needless to say, I was at a loss. Everything seemed to be in good working condition and I hastily pulled off the head for nothing. Over the next day I decided I'm just going to put it back together, but I chose to pick up new lifters just for some piece of mind. 

The next day my dad stopped by and I was showing him my progress on the truck. I kept thinking about the lifter that I wasn't sure if I tried to pull apart. So, I pulled the lifter out of the engine again tried to pull it apart, and it held. That's when I turned the roller over and saw that one side had been completely hammered flat by the camshaft! Surprisingly, the camshaft is still in pretty good shape, not nearly as bad as I would've thought. 

So there it is. Moral of the story, always THOROUGHLY inspect your parts! I hope someone finds this useful because I've never had this much trouble trying to diagnose a problem before. Thanks to forums like this one and some youtube mechanics, I was able to know what and how to pinpoint the misfire of P0301.

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