Question about 1991 Toyota MR2

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Knocking noise from AC compressor

At about 3000 RPM I hear a knocking noise from my 1991 MR2's AC compressor. This happens if the engine RPM is increasing or decreasing.

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I would replace the compressor, if it seizes up, the belt will keep turning over the pully and burn then snap

Posted on Jan 31, 2009

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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.

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On a 1991 olds ciero a non engine external knocking noise. could this be the air conditioner compressor?


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