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Dan, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2270
Experience:  20 Year Factory Trained Current GM Technician
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2002 chevy trailblazer: 4.2 i6, noisy engine..warms

Resolved Question:

2002 chev trailblazer 4.2 i6, noisy engine when cold starting and quiets down when it warms up but never goes completely away. Sounds like it is deeper than the valve train. Piston slap?
Submitted: 7 years ago.
Category: Chevy
Expert:  Dan replied 7 years ago.

When you say "noisey" , Can you describe the noise a little better?
I am guessing that when the belt off the noise was still there.
Is it a tick noise? Posible exhaust noise?
Are you losing any coolant?
Customer: replied 7 years ago.
yes a ticking noise, still there with the belt removed, not loosing coolant, great oil pressure, no oil consumpsion, normal operating temp, lots of power?? any history of piston slap in these engines?
Expert:  Dan replied 7 years ago.
Is it a single tick or like mutiple tick?
A tick every second or more?
Customer: replied 7 years ago.
The tick is relavent to the engine RPMs I would say it is only one cylinder, but not sure
Expert:  Dan replied 7 years ago.
I don't see many complants from these engines with the piston slap noise. I really don't remember ever hearing one complant of piston slap.
A couple of things I do see with these engines:

If it is a single tick about every second.This condition may be caused by the electro-viscous fan clutch control function of the Powertrain Control Module (PCM) attempting to keep the fan speed between 300-600 revolutions per minute (RPM). At idle, the cooling fan speed will drag to approximately 500 RPM then oscillate between 300 and 600 RPM. When the fan speed drops below 500 RPM, the PCM will pulse the fan control solenoid. The pulsing of the solenoid is the cause of the ticking noise. To confirm this, Unplug the connector to the fan clutch and see if the noise stops.The connector is on the drivers side by the radiator fan shroud. Reprograming the PCM calibration will fix this.

It could be the lash adjusters not getting oil.the oil gallery plug located between the number 1 cam journals may come out of position causing insufficient oil to the lash adjusters. This will result in a tick noise at all times from multiple lash adjusters.

It could be the timing Chain tensioner or chain causing a noise. Something could have broken or come loose or a worn timing chain guide.
Expert:  Dan replied 7 years ago.
I have replaced many Exhaust manifolds for being cracked and causing noise complants.
Sometimes the Exhaust manifold warps and breaks a bolt and could cause a noise.
Dan and 2 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.
Are the lash adjusters or timing chain tensioners extensive repair jobs that need to be performed by a GM technician?
Expert:  Dan replied 7 years ago.
Timing chain is a big job very diffucult and of course expensive. All depends on what exactelly it is.

The lash adjusters isn't that hard. But does require the intake manifold to be loosen or removed.It could be as simple as an oil gallery plug came out, not very much in parts but still the labor cost.

I would recomend someone with experence with these engines.