Beretta L4-121 2.0L (1987)
Idle Speed: By Symptom
Technical Service Bulletin # 8811
Date: 870401
Engine Idle - Minimum Speed Adjustment Procedure
Number:
88-11
Section:
6C
Date:
APRIL, 1987
Subject:
MINIMUM IDLE SPEED ADJUSTMENT PROCEDURE
Model and Year:1987-88 CAVALIER, CORSICA, BERETTA
WITH 2.0L (VIN CODE 1) ENGINE
TO:
ALL CHEVROLET DEALERS
The 1987 Cavalier and Corsica/Beretta preliminary shop
manuals describe a procedure to adjust the minimum idle
speed. The procedure involves grounding the diagnostic
terminal with the key on (engine not running) to drive the Idle Air Control (IAC) valve fully extended. This procedure should not be followed when
setting the minimum idle speed on 1987 2.0L 4 cylinder engines.
NOTE :
THIS ADJUSTMENT SHOULD BE PERFORMED ONLY WHEN THE THROTTLE BODY REQUIRES REPLACEMENT. COMPLETE TBI
UNITS ARE FACTORY ADJUSTED AND SHOULD NOT BE RESET AT DEALERSHIPS.
The 1987 Cavalier final service manual provides a new
procedure involving plugging the IAC valve air passage. In
addition, another satisfactory method for checking and/or adjusting the minimum idle speed has been developed. Either method is applicable to the 1987
Cavalier and current 1987-88 Corsica/Beretta with 2.0L engine. Both procedures are listed below.
PROCEDURE A (Shop Manual Revised Manual Method)
1.
Remove the T.B.I. bonnet and gasket.
2.
Pierce the idle stop screw plug with an awl and apply leverage to remove it.
3.
Connect tachometer to engine or use "Scan" tool to check engine RPM.
4.
Set parking brake and block drive wheels.
5.
Start engine, put transmission in park (neutral on manual transmission) and allow engine RPM to stabilize.
6.
Disconnect idle air control connector.
7.
Install tool J-36377 - Kent Moore or BT 8528A - Burroughs, or equivalent, in idle air passage of TBI unit. (Verify that no air leaks around the
tool).
8.
On vehicles with automatic transmissions, place selector lever in D (drive) before making adjustment.
9.
Adjust idle stop screw to obtain 650 +/- 25 RPM.
10.
On vehicles with automatic transmission, place selector lever in P (park). Turn ignition "off", remove IAC passage plug tool and reconnect IAC
valve electrical connector.
11.
Use silicone sealant, or equivalent to cover minimum air adjustment screw.
12.
Install TBI bonnet (replace gasket if necessary).
PROCEDURE B (Alternative Method)
1.
Remove TBI bonnet and gasket.
2.
Pierce the Minimum Air Adjustment Screw plug with an awl and apply leverage to remove it.
3.
Connect a "Scan" tool to monitor IAC counts and engine RPM.
4.
Set parking brake and block drive wheels.
5.
Put transmission in P (park), neutral on manual transmission, start engine and allow engine RPM to stabilize.
6.
Create a vacuum leak by removing a vacuum hose to a manifold vacuum source. Allow vacuum leak to remain until "O" IAC counts are shown on
"Scan" tool.
7.
With IAC counts at 0, disconnect Idle Air Control Valve electrical connector.
8.
Reconnect vacuum hose.
9.
On vehicles with automatic transmission, place selector lever in D (drive) before making adjustment.
10.
Adjust Minimum Air Adjustment screw to obtain 650 plus or minus 25 RPM.
11.
Turn ignition "OFF" and reconnect IAC valve electrical connector.
