ISC Valve - Rough Idle/Miss Under Load
Bulletin No.: 012/96Issued: 04/25/96
Revised:
Category
F
Applicable Model/s
1993 - 95 626/MX-6
Subject:
IDLE AIR CONTROL VALVE (ISC) SERVICE PROCEDURE
APPLICABLE MODELS/VINS
All 1993 - 1995 626 and MX-6 with a 2.0L (FS) engine.
DESCRIPTION
Rough engine idle or a miss under load may be caused by carbon accumulation inside the ISC valve. If a customer complains of these symptoms, use the procedure in this bulletin to identify the problem and, if necessary, remove the carbon. DO NOT REPLACE THE ISC VALVE TO CORRECT THIS CONCERN.
REPAIR PROCEDURE
1. Run engine to normal operating temperature.
^ On all 1993 2.0L and 1994 - 95 2.0L (MTX) vehicles, connect a jumper wire between the "TEN" and the "GND" terminals located inside the Data Link Connector. Refer to Fig. 1.
^ On 1994 - 95 2.0L (ATX) vehicles, remove the "Shorting Bar." Refer to section F3 of the workshop manual.
2. Verify engine idle speed.
^ If idle speed is not between 650 - 750 RPM adjust as necessary. Refer to the workshop manual for instructions.
3. Check engine timing.
^ If the timing is 11 - 13 degrees BTDC proceed to step 4.
^ If the timing is not 11 - 13 degrees BTDC, adjust the timing according to the instructions in the workshop manual, then proceed to step 4.
4. Disconnect the ISC valve connector.
^ If the engine RPM drops or the engine stalls, the ISC valve is functioning properly and does not require service. Refer to the workshop manual for troubleshooting information for causes other than ISC valve.
^ If no change in engine RPM occurs, the ISC valve may need cleaning. Proceed to step 5.
WARNING:
THE ISC VALVE MAY BE HOT, EXERCISE CAUTION TO PROTECT FROM BURNS.
5. Turn the engine off and remove the ISC valve.
6. Thoroughly mix 1 part (25 ml) of S.W. 1000 to 5 parts (125 ml) of water.
NOTE:
It is VERY IMPORTANT that a 1 to 5 ratio be maintained. Over strengthening or diluting will not produce the desired resuits.
CAUTION:
Wear Safety Goggles and Protective Gloves when working with and around this solution.
7. Pour the solution into the cavities identified as "A" and "B" in Fig. 2.
NOTE:
The solution must fill the cavity and cover the plunger completely. The plunger is the reddish, spring-like apparatus located in cavity "B."
8. Allow the solution to sit for FULL 15 MINUTES. If solution is not allowed to soak for at least 15 minutes, the repair will not be effective.
9. Dump the solution from the ISC valve in the direction of side "C" to avoid contaminating the BAC valve.
10. Apply compressed air for 20 second in each cavity to remove carbon deposits.
CAUTION:
Hold the ISC valve away from the face or exposed skin while applying compresses air. FOLLOW ALL MANUFACTURER'S PRECAUTIONS WHEN USING THIS AND ANY OTHER TYPE OF CHEMICAL.
11. Repeat steps 7, 9, 10. Do Not repeat step 8.
12. Connect the ISC valve to the engine harness.
NOTE:
Make sure the ignition key is in the "OFF" position.
13. Hold the ISC valve and watch the plunger (cavity facing toward you).
14. Have an assistant turn the ignition to the "ON" position. DO NOT CRANK ENGINE, COOLANT LEAKAGE WILL OCCUR.
^ If the plunger moves open and closed quickly, proceed to step 15.
^ If the plunger does not move open and closed, disconnect the ISC valve and repeat steps 7 through 14.
15. Rinse the ISC valve (cavities "A" and "B") 2 or 3 times with water.
16. Repeat step 10 to remove any remaining deposits and water.
17. Install the ISC valve with a new gasket.
18. Verify repair using steps 1 - 4.
19. With the engine at normal operating temperature, cycle A/C, headlights and rear defroster on and off.
^ Engine idle should remain stable or RPM increase slightly to compensate for the additional load.
^ If the engine RPM drops, the problem is not the ISC valve. Refer to the workshop manual for additional troubleshooting information.
PARTS INFORMATION
WARRANTY INFORMATION
(Applies To Verified Customer Complaints On Vehicles Covered Under Normal Warranty. Refer To The SRT Microfiche For Warranty Term Information.)
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