Engine - Vibration at Idle
BULLETIN NO.: 95-T-36ISSUE DATE: August, 1995
GROUP/SEQ. NO.: Engine-07
CORPORATION NO.: 586002
SUBJECT:
Objectionable Engine Vibration at Idle (Check Cooling Module Mounts, Engine Strut Cradle Bracket, Muffler Hanger and Strap, and Adjust or Replace as Required)
MODELS AFFECTED:
1994-1996 Saturns
CONDITION:
Some customers may comment about objectionable engine vibration at idle. This condition may be more noticeable when the engine reaches normal operating temperature.
CAUSE:
Objectionable engine vibration at idle may be caused by one or more of the following conditions:
^ Engine not idling properly.
^ Improper positioning of upper cooling module grommets; lower cooling module not seated; improper positioning of A/C wiring harness.
^ Preloaded engine strut cradle bracket.
^ Improperly positioned muffler hanger and strap.
IMPORTANT:
The rubber isolation cushion in the engine mount has been improved on all 1994 through 1996 vehicles. The engine mount should not cause objectionable engine vibration at idle.
CORRECTION:
Refer to Procedures to diagnose and repair any condition that could cause objectionable engine vibration at idle.
Some level of engine vibration is normal during initial engine warm-up. Engine idle vibration quality should be evaluated only when the engine reaches operating temperature and when the engine maintains a stable RPM. Before evaluating engine idle vibration quality, road test the vehicle and verify that the condition is present with the engine at operating temperature. Using a portable diagnostic tool (PDT), make sure the engine's ignition and fuel systems are functioning properly. If the engine is not running properly, repair as needed.
PROCEDURES:
Vibrations are normally felt in the steering wheel, lower seat cushion, seat back, or floor pan Vibrations should be diagnosed with the vehicle stopped and the transaxle in Drive ("D") for automatic transaxles and in Neutral for manual transaxles. If the vehicle is equipped with A/C, make sure the A/C compressor is OFF.
Check Cooling System Grommets
1. Make sure the lower cooling module mounts are properly seated in the pockets of the cradle.
2. If the vehicle is equipped with A/C, check the radiator air upper seal and wiring harness along the forward side of the tie bar for correct positioning. If the wiring harness is not positioned properly, remove the upper radiator brackets and perform the following steps:
a. Position the lamp wiring harness forward of the radiator air upper seal.
b. Position the radiator air upper seal back into the cooling module slots
3. Check the upper cooling module grommets (located in upper radiator brackets) for binding, for misalignment, and for freedom of movement. The cooling module retaining pins must be centered in the grommets for support by the upper radiator bracket(s), and the cooling module should move from left to right, forward and rearward freely a minimum of 3.18 mm (1/8 in.). If the grommets are pinched, loosen the upper radiator bracket(s) and reposition them. Make sure the locator tang in each upper radiator bracket is properly positioned in the upper tie bar slot.
4. Tighten the upper radiator bracket(s) fasteners. Check the cooling module for freedom of movement.
Torque: 10 N-m (89 in-lbs)
IMPORTANT:
The cooling module must move freely both left and right as well as forward and rearward a minimum of 3.18 mm (1/8 in.).
Check for Preloaded Engine Strut Cradle Bracket
Loosen the two engine strut bracket-to-cradle fasteners and check the powertrain for binding by pushing forward and rearward on the engine oil pan. The powertrain should travel a minimum of 3.18 mm (1/8 in.).
If the powertrain does not move, perform the following procedure:
1. Check the engine and transaxle struts for correct installation and bushing wear.
2. Check the engine strut bracket-to-cradle fasteners. Refer to "Engine Strut" procedure in the "Powertrain Mounts" section of the "Chassis Service Manual."
3. Shake the powertrain by pushing forward and rearward on the engine oil pan.
4. Allow the powertrain to settle to its natural position; tighten the two engine strut bracket-to-cradle fasteners.
Torque: 50 N-m (37 ft-lbs)
IMPORTANT:
Make sure the engine strut bracket does not move forward or rearward when torquing the two fasteners.
Check the Muffler Hanger and Strap
Check that the muffler can be moved both vertically and horizontally in the muffler hanger. The muffler should move in the muffler hanger a minimum of 1.60 mm (1/16 in.) vertically (direction A) and 3 mm (1/8 in.) horizontally (direction B).
If the muffler does not move freely, perform the following procedure:
1. Loosen the muffler strap and position the muffler to allow the movement described above.
IMPORTANT:
Two rows of bumps have been formed in the muffler sheet metal; the muffler strap must be positioned between these two rows of bumps.
2. Tighten the muffler strap and check for specified vertical and horizontal movement as stated above.
Torque: 31 N-m (23 ft-lbs)
IMPORTANT:
If the specified muffler movement cannot be obtained, carefully lower the exhaust system and adjust the muffler hanger using washers. Washers with an inside diameter of 9.53 mm (3/8 in.) can be installed on the attachment bolt(s) between the muffler hanger and the frame rail to align the muffler hanger parallel with the muffler.
3. To lower the exhaust system:
a. Remove the intermediate exhaust pipe (center) insulator and the muffler strap fastener; carefully lower the exhaust system.
b. Loosen the muffler hanger fasteners and inspect the muffler hanger and frame rail surfaces for debris.
c. Clean the surfaces or rotate the muffler hanger to align it with the muffler strap. If necessary, install washers between the muffler hanger and the frame rail to align the muffler hanger parallel with the muffler.
d. Tighten the muffler hanger fasteners and the muffler strap fastener. Check for sufficient muffler movement, as previously described.
Torque Muffler Hanger Fasteners: 18 N-m (159 in-lbs)
Torque Muffler Strap Fastener: 31 N-m (23 lbs. ft.)
CLAIM INFORMATION:
To receive credjt for this repair during the warranty coverage period, submit a claim through the Saturn Dealer System using the appropriate Electronic Labor Time Guide for the correct Labor Operation Code and Time.