Engine Controls - Idle Shake Correction
Model Year 1983Bulletin No.. 83-227
File in Group 64A
Number 25
Date April '84
SUBJECT: IDLE SHAKE CORRECTION
MODELS AFFECTED: 1983 SKYLARKS 2.5L (ENGINE CODE R) EQUIPPED WITH (1226100) 2 BOARD ECM)
We have heard of some comments of idle shake on subject vehicles. Several or a combination of possible contributors listed in this bulletin may cause this condition.
Items to be checked prior to the installation of the PROM listed in this bulletin should be inspected and, repaired as required prior to release of vehicle to the customer.
1. Power steering hoses contacting the a/c accumulator have a significant effect on instrument panel vibration at idle. Also heater hose and clamp contacting heater module, or any other lines touching the cowl when in drive. Insure that all hoses and lines are pulled away from accumulator and front of cowl so that no contact occurs.
2. Engine cradle aligment will influence idle quality. The cradle should be properly aligned using following procedure:
a. Support vehicle on suitable lift or stands at the (4) lift points indicated in the Chassis Service Manual, Section 0, Maintenance and Lubrication.
b. Loosen all (4) cradle to body attaching mounts.
FIGURE 5:
FIGURE 6:
c. Align cradle to body by inserting 2 pins (16 mm (5/8") dia. by 8" long in alignment holes an right side of cradle (Figure 6). Tighten body mounts to torque specified in Figure 5. Alignment pins must not be removed until all body mount bolts are tightened to specified torque.
NOTE: Torque sequence of cradle mounts 4,3,1,2. See Figure 5.
d. Loosen upper engine to radiator torque strut support bolt, radiator side (hole is slotted) with parking brake applied and front wheels blocked, put transmission selector in drive at idle and torque strut bolt to 35 ft.lbs. or 48 N-m.
FIGURE 3:
3. Excess rubber in either or both of the transmission mount interlock windows will influence idle vibration (See Figure 3 . This rubber, if present, should be cut away with the mounts on the vehicle.
FIGURE 4:
4. Check for an unrelaxed rubber exhaust hanger rearward of the catalytic converter (See Figure 4). The unrelaxed hanger will transmit vibration through the floor pan and body structure. If this condition exists, loosen the exhaust joint ball flange, reposition the catalytic converter upwards to unload the hanger and retighten the exhaust system flange bolts to 15-17 ft.lbs. or (20-24 N-m). Visual checks for exhaust system contacting the body should also be made.
5. Loose, improperly installed, or missing instrument panel fasteners will also contribute to idle vibration.
FIGURE 1:
FIGURE 2:
A recalibrated PROM has been released for service which raises the idle speed to 800 rpm for idle shake improvement. This should be installed only after all other above items have been checked and corrected.
To determine which PROM applies to the vehicle being serviced, determine the correct axle ratio by referring to the transmission code identification plate as illustrated in Figures 1 and 2.
This new PROM is to be used only an vehicles equipped with two (2) board ECM's, (part number 1226100), per the following chart.
ECM PROM BROADCAST TRANSMISSION AXLE
USAGE NUMBER PROM CODE CODE RATIO
1983 1226100 1226828 CDL PW 2:39
2.5L Auto Trans. National
1983 1226100 1226827 CCY PD 2:84
2.5L Auto Trans. National