bigtower2003

This is my first post; I was a ford man until now. I recently purchased a 2005 Chevy Tahoe LT (5.3L) with 30k miles (GM certified). I noticed the other day while in the car during idlethere was strange rattle, not loud and similar to a morse code machine (dot, dot, dot, etc.). I watched it for the next couple of days and noticed the following:

[ul][*]the rattle is particularly loud when I shut of the engine and when I first turn it out.[*]I can only here it when all the doors are closed and there is no music on and the car is in park.[*]I can only here when in idle; as I increase the RPMs it goes away but always returns when it goes back to idle.[*]I hear the noise with the AC or heat off.[*]The noise is persistent throughout, not just during cold starts[/ul]
Is this normal engine noise? I have never heard this in my fords, partially because they never ran, but when they did run I never heard this noise. Any ideas?

73shark

Welcome to the Tahoe forum.

Are you saying that the noise is there as you shut the engine off or after the engine is off?

If the former then it might be a sticky lifter. If the three year warranty hasn't expired, I'd get it in to the dealer's service.

What does it sound like if you are outside w/ the hood up?

Had another thought, it could be an exhaust leak. That makes a ticking sound.

bigtower2003

Thanks for the response. The ticking only occurs as I shut the engine off, it does not tick when the engine is off. When I pull up the hood I don't here anything, it's strange but I only hear it while sitting in the car with the door close. When I open the door I can't hear anything. What do you think it could be, the lifter?

in2pro

Can anyone else hear it and what does it sound like to them? sometimes hearing different descriptions of the same sound can lead you to it.
Onlyhearing it on the inside could it be the A/C vent loosing vacuum and creaking shut ?

bigtower2003

my wife thinks it sounds like a rattle and my dad describes as a muffled rattled similar to what it sounds like when someone with heavy chest congestion is breathing and you can hear the phlegm in their chest.

in2pro

Im still leaning toward the ventaltion system since you only hear it inside the passenger compartment and when you first shut it down.
What is the duration of the sound?
gone in a few seconds?
does it sound mechanical?
metal or plastic?
sharp or dull?
only happens when you do this or not that?
left side right side in the center?

ZX1100F1

Sounds like it could be the O2 sensor connecter resonating against the underside body of the vehcile, this normally makes a sound simliar to what you have described and goes away when the engine is rev'd just above idle (800-900rpm).
The fix is to install a new connector mounting clip GM P/N 12110783 ( this updated clip has an anti-rattle feature) between the right rear O2 sensor harness and the under side of the cab.

bigtower2003

jeff; it doesn't just do it on first shut down but all shut downs--as far as duration it persists as long as the engine is on--sounds plastic--don't think its mechanicl--sound is dull--it happens on drivers side only

Daven thanks for the response, is the retainer on the drivers side?

in2pro

Sorry my bad, I was under the impression that it only happened AFTER you turned the engin off. Reading is fun-de-mental....

ZX1100F1

The retainer is on the pax side rear O2 sensor, you'll see what it's all about if you climb underneath and take a peak.