Engine - Knocking Noise At Idle

Classification:
EM94-001

Section:
Engine Mechanical

Models:
M30, J30

Reference:
TECHNICAL BULLETIN ITB94-046

Date:
August 18, 1994

M30 AND J30 ENGINE KNOCKING NOISE

SERVICE INFORMATION

Some M-30 (F31) and J30 (JY32) model vehicles may exhibit an engine knock noise at idle after full warm up. This noise on incident vehicles may be eliminated by replacement of the engine # 1 main bearing with one of the next thickness grade higher (reducing the main bearing clearance for the # 1 main bearing).

SERVICE PROCEDURE

When an engine knocking noise at idle is suspected, repair the vehicle using the following procedure:

1) Confirm the knock noise and the location. The noise is most noticeable at idle speed or slightly above idle, with the transmission in "P" or "D" range (vehicle stationary) and the engine fully warm. The noise will be most noticeable in the vicinity of the # 1 main bearing when listening with a stethoscope (vehicle on a lift).

2) Note if the noise is eliminated by cancelling the # 1 cylinder using CONSULT ("Power Balance" test in "Active Test" mode) or by reducing the accessory drive belt tension, proceed with the next step. If the noise is not eliminated, call the Infiniti TECH LINE.

3) Once the incident is confirmed to be from the # 1 main bearing (through the tests in steps 1 & 2), remove the bearing and replace it with a bearing "one" thickness grade number higher (a thicker bearing, which will reduce the oil clearance).

4) Using Plastigage or another suitable method, confirm that the clearance for the # 1 main bearing is within specification, 0.0011-0.0022 inch (0.028-0.055 mm), and reassemble the engine.

5) If the engine knock is not eliminated, call the Infiniti TECH LINE.





PARTS INFORMATION:





WARRANTY INFORMATION: