Cylinder 7 low compression

Javy · December 28, 2019

Hy guys I'm new to the page hoping to find some answers. I have a 2014 chevy Silverado ltz 5.3 with low compression on number 7 cylinder it all started leaving a restaurant from having dinner I mashed on it hard pulling into the highway and the engine light started flashing and stabilitrac lights came on made it home and parked it next morning I hooked my scanner up and seen #7 was misfiring so I pulled the plug to inspect it and it had a little bit of oil on it and looked old so I went ahead and replaced them all and nothing changed so I swapped coil and wire with #1 and the misfire didn't change so right away I thought a afm lifter failed so I pulled the valve cover of and both rockers where moving fine so did a compression test and only get about 25 pounds at idle so today I decided to pull the head off and inspect the piston cylinder and lifters and everything seems fine valve and springs seem fine to besides some carbon buildup so now I don't know what direction to go hopefully some one here can point me in the right direction also cam lobes look good too

Ozer · January 8, 2020

What did you end up doing with this issue?

What year and miles are you, under warranty?

BigBadSierra · January 8, 2020

Cylinder 7 is an AFM cylinder so most likely a lifter failure.

Ozer · January 9, 2020

21 hours ago, BigBadSierra said:

Cylinder 7 is an AFM cylinder so most likely a lifter failure.

he said " I thought a afm lifter failed so I pulled the valve cover of and both rockers where moving fine " so it may not be the case.

BigBadSierra · January 9, 2020

32 minutes ago, Ozer said:

he said " I thought a afm lifter failed so I pulled the valve cover of and both rockers where moving fine " so it may not be the case.

It may not be locked but sticking so it’s letting cylinder pressure drop. They don’t always collapse. If it is sticking it will eventually get stuck and collapse.

avidsailor · January 20, 2020

I did not have any codes but my mileage went sideways. My mechanic stated that it is an internal problem and that I need to have the engine rebuilt.

Timothy0159 · February 11, 2025

I seem to have a similar problem with my 2011 Cadillac Escalade EXT. compression test shows about 42 on number 7 but the rest have around 54-57 while running. Someone told me to put a can of trans fluid into the oil and run it a while and it may loosen up the sticky lifters. If anyone sees this, what are your thoughts?