JJB

I have a misfire in cylinder 6. I checked the plugs, wires and coil all are fine. I had a 99 Lumina with the same code and it was the injector . So I decided to go ahead and replace it. Well, that didn't fix the problem.

I did a compression test (should have done that first). I get 20-30PSI in 6, 90PSI in 2 and 150PSI in 4. 4 is in the middle.

Is this a head gasket issue? A bad valve/warped head? Or worse bad rings or piston?

The oil looks clean and so does the coolant but I have noticed that the coolant seems a little low.

Are there common problems that would cause this?

Any help is greatly appreciated.

MDTAHOE

You would need to perform a cylinder leak down test to pinpoint the problem.

JJB

Is there a way to do this without buying a leakdown tester?

JJB

I decided to starting tearing it down today. But first I wanted to remove the valve cover just to see if there were any tell tale signs there.

I couldn't believe what I found. Both #6 rocker arms were just laying there. The threads were ripped out of the head. Unblievable!!!

I tried searching the web for solutions but pretty much knew there were really only 2. Heli coil or new head. I opted for the Heli coils and red loctite. Now she is running nice and smooth with no codes.

A web search yielded many similiar problems with the 3.4L engines in various vehicles.
This looks like a defect to me. I wonder how long it will take for another one to fail?

I read that in 2003 they changed the heads to use 8mm bolts instead of 10mm. That seems like a pretty stupid idea as there is very little area to hold in the soft aluminum head.