Code P0301, misfire cylinder 1?

LOPEN

MEMBER
2007 CHEVROLET SUBURBAN
5.3L
V8
4WD
AUTOMATIC
177,000 MILES

Changed all plugs and wires also the coil for cylinder 1,

have cleaned the MAF filter, throttle body, and EGR valve.

no other codes.

RPMs fluctuate erratically and the vehicle has been dying when slowing for turns or stopping at lights etc.

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,256 POSTS

It sounds like you have low compression in the #1 cylinder but to be sure please go over this guide:

https://www.2carpros.com/articles/how-to-test-engine-compression

Please go over this guide and get back to us.

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Tuesday, September 12th, 2023 AT 10:36 AM

LOPEN

MEMBER
2 POSTS

Checked compression in cylinder 1 and 2. Cylinder 1 registered at 90 PSI, cylinder 2 registered at 150 PSI, did a second test and there was 0 compression in cylinder 1. Cylinder 2 spark plug was covered with carbon soot when I took it out. Cylinder 1 spark plug looks fine. Smells gassy though.

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Wednesday, September 13th, 2023 AT 4:48 PM

KEN L

MASTER CERTIFIED MECHANIC
47,256 POSTS

Yep, you have found the problem, it sounds like the intake valve is leaking or damaged. I would remove the cylinder head for inspection. Check out the images (below). Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.

Images (Click to make bigger)