Hi All, long time observer here but ran into an issue in the past few weeks and trying to diagnose. Came back from a road trip on my 2016 Suburban LTZ w/5.3 engine and noticed a ticking sound. A few things about the sound:

1) I hear it within a minute of driving the car after cold start and it doesn't go away after continuing to drive
2) It only happens when the car is under load and accelerator is down (lightly or aggressively)
3) It increases frequency with RPMs but drowns out at higher RPMs
4) It's most pronounced when lightly accelerating 1-2k RPMs
5) Zero ticking / chirping at idle and when revving in neutral or park; the only way I can recreate is when I power brake and apply the accelerator

Took it to my mechanic and they thought lifters at first, but looked at other potential things since there weren't any sounds at idle. They did find that when spraying the intake manifold with liquid, they got one area showing fuel trim levels that were spiking lower than all other areas. We replaced the intake manifold but still getting the sound, and now they're saying we could try the O-rings on the fuel injectors since that was downstream. Overall, they say there is something going on given the fuel trim readings (essentially a leak somewhere), so I'm debating on whether to go further or ask them to look at other things.

This trigger any ideas for anyone out there? If I take the car back I can upload a video of the sound. Thanks all for any input.

John

 

well a vacuum leak would cause crazy fuel trims, but not noise.

Ticking could be AFM induced lifter failure.

A video with good sound might help

 

Thanks Joe. The mechanic brought in a master technician, whom apparently suggested the o-ring path as he said he's seen similar situations where there was a compression leak past the worn injector rings. Hoping this will in fact be the case but should find out late this week.