Replacement motor questions but hopefully fixable

[rockdogz]

So I swapped injectors with cylinder 2 and the P0304 came back - cylinder 4 misfire. I also pulled the valve cover and all rockers are moving up and down. Not sure where to go from here.

 

[Rocket Man]

So I swapped injectors with cylinder 2 and the P0304 came back - cylinder 4 misfire. I also pulled the valve cover and all rockers are moving up and down. Not sure where to go from here.

Is the harness swappable?

 

[rockdogz]

Is the harness swappable?

I think so, I will try.
If it was a cracked head then would the cylinder hold compression?

 

[rockdogz]

I can swap the coil harness but not the injector harness

 

[Rocket Man]

I think so, I will try.
If it was a cracked head then would the cylinder hold compression?

Pretty sure it would depending on where it’s cracked.

 

[rockdogz]

Swapped the coil harnesses and misfire on cylinder 4 still. It sounds like a lifter based on a YouTube video I saw where they had a bad lifter. Just not sure why the rockers are still moving then.

 

[wsteele]

Swapped the coil harnesses and misfire on cylinder 4 still. It sounds like a lifter based on a YouTube video I saw where they had a bad lifter. Just not sure why the rockers are still moving then.

Exhaust leaks can sound like a lifter tapping. Not the cause of your misfire if it is, but it could be where the sound is coming from. You might check to make sure all your exhaust manifold fasteners are still there and check closely for exhaust leaks.

 

[89Suburban]

Did you pul

Swapped the coil harnesses and misfire on cylinder 4 still. It sounds like a lifter based on a YouTube video I saw where they had a bad lifter. Just not sure why the rockers are still moving then.

l the spark plug? Just curious, missed a lot in this thread.

 

[rockdogz]

Did you pul

l the spark plug? Just curious, missed a lot in this thread.

Yes I was due for a a tune up anyway and have new plugs, wires, coils. The cylinder held compression and the rocker arms move when engine cranks and are not loose. Tried swapping injectors and misfire always on 4.

 

[wsteele]

So you have fire (spark), compression (compression tested good) and you have fuel (jury still out on the injector harness), so theoretically you shouldn't have a misfire.

The injectors make a distinct clicking sound when firing. Take a stethoscope (or long screwdriver you can get your ear on the end) and put it on a few injectors while the engine is running. You will hear the clicking as they fire, then move to the #4 and make sure it also gives you the clicking sound. If it doesn't then you have a wire connector/harness issue. If it does, then you know you are getting gas.

With gas, you only have mixture left. That could be a leak in the intake. If you get that far and it isn't the injector harness, try taking some carb cleaner and spray around the intake manifold at #4. If the engine speeds up in idle and smoothes out, you have an intake leak.

EDIT: The intake manifold on these trucks is plastic, so instead of carb cleaner, maybe pick up some of that CRC intake manifold test spray can stuff. Carb cleaner is pretty aggressive stuff, not sure what it might do to the plastic manifold.

That is all I got.

 

[Fless]

Couldn't an exhaust leak cause a misfire?

 

[89Suburban]

Couldn't an exhaust leak cause a misfire?

 

[wsteele]

Couldn't an exhaust leak cause a misfire?

I have never had an exhaust leak cause a misfire (at least one that leaked at the exhaust manifold). But maybe, I guess depending on the valve timing.

 

[rockdogz]

I checked the exhaust bolts and they seemed tight.
I’m leaning towards pulling it apart to check the lifters/heads/intake

 

[wsteele]

I checked the exhaust bolts and they seemed tight.
I’m leaning towards pulling it apart to check the lifters/heads/intake

Did you verify with an audible test that number 4 injector was firing?

 

[wsteele]

Also, I would do the intake manifold leak test with that CRC intake manifold aerosol stuff. If you have an intake leak, it likely will show up with it.

 

[BobBilly]

So I seem to have a blown (and not blown as in supercharger) up 5.3 in my 2008 Tahoe. It just happened but I think it’s a spun rod. I had been planning to research engine swaps but this came at a bad time so I just want to swap in a remanufactured engine.
should I go for another 5.3 or is there a straightforward swap or kit for something larger (6.0?) or newer? I need something that’s already sorted out and will be smog legal in CA.
Any and all suggestions on someplace that could hook me up would be most appreciated!
Thanks
Tom

 

[BobBilly]

I
have a 2005 Yukon XLT LOADED andwas in good conditio, it was my daughter’s and her husband was going to Trade it in for $2300, with 180,ooo miles. I decided to buy it from him and put a new engine in.
I bought a rebuilt “Long Block”, from Rockauto.com for $1650.00 I put it in my self and then had a rebuilt transmission installed for another $1,650.00. It has been 19 months and I am very pleased to have a like new SUV for much less than buying a new one. Even if you have to pay a shop to put the engine in for you, about $1,000.00, you still come out better than buying a new SUV at the prices today, if you can actually find one.

 

[Rocket Man]

I
have a 2005 Yukon XLT LOADED andwas in good conditio, it was my daughter’s and her husband was going to Trade it in for $2300, with 180,ooo miles. I decided to buy it from him and put a new engine in.
I bought a rebuilt “Long Block”, from Rockauto.com for $1650.00 I put it in my self and then had a rebuilt transmission installed for another $1,650.00. It has been 19 months and I am very pleased to have a like new SUV for much less than buying a new one. Even if you have to pay a shop to put the engine in for you, about $1,000.00, you still come out better than buying a new SUV at the prices today, if you can actually find one.

Why did you put in a new engine? Unless it was badly mistreated it was good for another 200-300,000 miles. 4-500,000 miles isn't uncommon for the LS based engines.

 

[TollKeeper]

Can we back up a minute?

I understand you swapped coils, but did you verify spark was actually going across the strap at the spark plug?

Other than a collapsed lifter, you have ruled out pretty much everything else. So now it's a matter of verifying the result.