Dropped #4 piston?

[dbobway]

Bob Douthit

[dbobway]

I'm new, please excuse my lack of PC knowledge.

I have a 2008 Suburban LS 4x4 1500 5.3 146,000 miles.

Drove great a month, engine light came on p0304, 

Changed the plug, coil, spark plug wire plus fuel injector, on #4 cylinder.

No help. I felt like I was getting no spark from the wire harness or the computer.

It doesn't knock. Runs fine, but rough. Took it in to the shop, they said I dropped a cylinder, only had 20 LBS. of pressure, on piston #4. I have a written maintenance history, looks pretty thorough.

I've been driving 350 GM trucks for 40 years in all kinds of conditions. This didn't pass the smell test.

Looking for some advice. Thanks

[It's Tim]

Perform a leak down test yourself.

[CamGTP]

Cylinders 1, 4, 6, 7 are AFM/DoD cylinders. If the AFM lifter failed it can cause that cylinder misfire.

[dbobway]

Hi Cameron,

I saw a video where they took off the valve cover and one of the rocker arms wasn't moving with the engine running. When they removed the rod, it was inoperative, and the cam was fine. They replaced the rod,  and it was fixed. The automotive shop said my cam is damaged. My knowledge says my engine wouldn't run that way. It runs like I have a bad coil on the #4 cylinder, and it just runs like it's missing.

Thank You for the tip. I have a 2001 suburban with 327,000 miles on the original engine. It runs great.

Thanks again Bob

[dbobway]

Thanks Tim, that is just what I'm going to do.