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2003 6.0L rough idle

warrab

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warrab Enthusiast

warrab

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I've got a rough idle with random misfire code. I also had lean codes on both banks so I changed the intake gasket and that was taken care of. The engine runs fine it's above 1500 rpm. I've read that it could be a broken valve spring so thought I'd take off the valve covers for a look. I did a compression test on it first and found two basically dead cylinders and two low ones. They're the back two cylinders on both banks and each side has a dead cylinder. I took off the valve cover and the rockers and valve springs look fine. I removed the rockers from one of the dead cylinders and decided to crank the engine to see what would happen and got 130lbs up from 10lbs. Could the valve springs be weak? There is 410,000 km on the engine. Anyone got any ideas? I've never come across this before.

Chris Senior Enthusiast

Chris

Posted
Posted

With those miles, it wouldn't hurt to do a tear down. Pull the heads, have a valve job done, inspect the pistons and cylinder walls for scoring, replace springs, new head gaskets, plugs, and wires. Refresh the engine.

warrab Enthusiast

warrab

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With those miles, it wouldn't hurt to do a tear down. Pull the heads, have a valve job done, inspect the pistons and cylinder walls for scoring, replace springs, new head gaskets, plugs, and wires. Refresh the engine.

That's what I'm thinking might be one option but I'd like to fix this with the least $$ possible. It's strictly a work truck and just needs to get me to the job and back. Don't need it to run great but just run. With the miles on it I'm going to be getting into trans issues soon as well so I just want to make it last a few years if possible. The intake valve I can actually press down with my hand slightly so I'm thinking it's the springs. Anyone know where I can get springs beside the dealer?

Chris Senior Enthusiast

Chris

Posted
Posted

gmpartsdirect.com if you have the part number. ebay possibly, could always go aftermarket

txab Senior Enthusiast

txab

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Most competent auto parts stores will have what you need. NAPA for example

  • 2 weeks later...
warrab Enthusiast

warrab

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ok, so I finally had a chance to pick up some springs and change them but the problem is still the same. Does anyone know if these engines have lifter issues? It's the only thing I can think would cause this. Cylinder has compression with the rockers off but nothing when installed. I'm thinking it's broken inside the lifter which is causing a valve to stay open slightly. Anyone have any ideas?

warrab Enthusiast

warrab

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Went back out and loosened the rockers off, then tightened them finger tight. Cranked it over and got 185lbs. Tighten the bolts and I get 10lbs. I think lifters.

Chris Senior Enthusiast

Chris

Posted
Posted

I think they are hydraulic roller lifters. If you no go that far, have the heads looked at and cleaned up

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