Hi, This is my first post about my 02LTZ Trailblazer 4X4. I have been having cold start noise that sounds like lifter noise that diminishes as engine warms up. Oil and filter at 3k or before, tried several additives, Techron, GM's additive, Sea Foam, Wynns Along with Rislone oil. Have tried different weight oil--no difference. I don't think it's pre-ignition as it starts cold at idle, and continues for about 3 to 4miles almost goes away. Also filled several times with different brands of top named premium fuel. I would think all carbon is gone as also have had Wynns injector cleaning along with the sea foam additive. The noise comes from top center of engine possibly more on passenger side. I checked manifold heat shield and found bottom
nut missing, I repaced it but NO change? Fan clutch seems to work
properly, with no play or noise. I keep up on all maintenance on or before recommended service.
Oh, isanyone having noise going over ruts in road? Look at sway bar links front and rear.Mine did not seem to have any play in them, but that was the problem as I switchd toMoog brand-- no noise at all! Thanks for your time. LTZ02

 

sounds like valve lash noise from rocker arms. check for proper adjustment

 

I had a 2002 TrailBlazer and it sounded like a diesel when it was cold, especially in the winter. GM said it was normal piston slap. Never had any problem with it and sold it with about 40K mi on it.

 

Hi, Thanks for the post on the T/B--I have tried about everything
to correct the problem short of possibly a NEW CAR. Just finished
changing the oil again at 3K --- only this time 5/30W semi/syn, one thing the engine is sooo clean even after 650 miles it's had to see
the oil on the stick. Added Lucas additive to it this time, but no
improvement. Been with GM. a along time and second car had a
problem with engine related. The other being a Buick Regal 3.8
that came with crank ground slightly undersized and it would produce light rod noise warm. Was a new car, and dealer covered
it, stating a TSB that if customer complains they would cover it.
Why would GM produce a engine that they hoped would bite them[]??? Back to subject at hand as soon as I add a can of piston
reeesizer I'll let you know.
Thx, LTZ02