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Chevrolet Uplander 3.9L intermittent knock until warmed up

On a 2009 Chevrolet Uplander with 3.9L engine, 44,000 miles, has an intermittent engine noise like a knocking and it goes away when the engine has warmed up - do you know what might be causing this, or does anyone else have this problem?

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  • Cars & Trucks Master
  • 818 Answers

Could it be a high pitch knocking like a ticking-this would be a lifter thats not pumping up right any-it may be time for oil change to winter oil-5w20-oil change could help anyway-cheers Denny

Posted on Nov 19, 2013

Testimonial: "maybe a lifter but it has synthetic oil now and did it when it wasn't so cold also - thanks"

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Posted on Jan 02, 2017

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  • 66 Answers

SOURCE: IN THE MORNING FIRST START SOUNDS LIKE TAPPING AND KNOCKING NOISE

ck intake gaskets make sure there is no antfreze mixing in oil and breaking oil down if gakets are ok run a factory oil filter and go up agrade in oil such as 10w40

Posted on Dec 17, 2008

  • 1 Answer

SOURCE: Engine make Knocking noise when cold

I have the same problem on my 2.0L 2001 Legacy auto. It began about 1000 miles ago. It has now done 84k. From my online searches this is most probably 'piston slap', and is not serious. To save weight Subaru shaved down the skirts on the pistons. With normal engine wear the pistons will at some point rattle against the cylinders until the engine is heated up and the pistons expand. The rattling should go away after a few minutes. If it persists say 10-15 minutes, it may be another problem.

Posted on Nov 26, 2009

ZJLimited
  • 17970 Answers

SOURCE: Infiniti G35 - 2006 Sedan

Smoke on start? Could be a valve problem where all your oil is in the bottom at start? Belts are squeaking too? Maybe a tensioner went bad?

Saw this service bulletin---

TAPPING / KNOCKING NOISE FROM ENGINE AT COLD START
This bulletin amends ITB02-049. This version amends the Applied Vehicles.
Please discard all paper copies of the earlier version.
APPLIED VEHICLE: 2002 - 2004 Q45 (F50)
2003 - 2004 M45 (Y34)
2003 - 2004 FX45 (S50) with V8 engine.
IF YOU CONFIRM:
A tapping or knocking noise (similar to a piston or valvetrain noise) when starting a cold engine,
NOTE: The engine is considered “cold” when it has been OFF (not running) for several hours.
ACTIONS:
1. Dislodge and remove any carbon deposits that may have caused the noise and confirm that carbon
deposits were the cause of the noise.
• While the noise is occurring, quickly rev the engine several times to approximately 4,000 RPM. Then
release the accelerator quickly, as soon as the engine reaches 4,000 RPM.
• The noise should disappear immediately if carbon deposits are the cause.
NOTE:
• If the customer reported a noise that exactly matches the symptoms listed above, but you cannot
duplicate it, the cause may still be carbon deposits. Go to step 2.
• If the noise does not stop after revving the engine, or you observe any other noise that doesn’t match
one described above, go back to ASIST for further diagnostic and repair information.
2. To prevent this incident from occurring again, add a bottle of Nissan In-Tank Fuel System Cleaner
P/N 999MP-FSC00P to a full tank of fuel (in the vehicle’s fuel tank) according to the instructions on the
label.
• This product is proven to reduce carbon deposits on pistons and combustion chambers, as well as
cleaning other components of the fuel system.

Hope helps.

Posted on Sep 08, 2010

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