Ajuste IAC and TPS

General Moto rs Reference

G067

Subject:

Minimum idle speed adjustment and idle air control (IAC) valve minimum air rate adjustment adjustment for fuel-inject fuel-injected ed engines engines

Symptom: Erratic or incorrect idle speed Source:

GM divisional service manuals This reference provides instructions for checking and adjusting the minimum idle speed (also called IAC minimum air rate) for most GM fuel-injected engines through the 1999 model year. When directed to this reference by a Fast-Track® Troubleshooter tip or by another reference in this manual, locate the engine displacement, model year, and engine code of the vehicle in the following tables. Table G067-1 G067-1 lists passenger car engines; Table G067-2 G067-2 lists lists truck engines. Each table includes the minimum idle rpm specification and directs you to the following procedures: •

•

through K contain instructions instructions for Minimum idle speed procedures —procedures A through establishing establishing the minimum idle speed of the engine for checking and adjustment. through 18 contain the the instructions that that must be Idle learn procedures —procedures procedures —procedures 1 through followed to ensure that the ECM adaptive memory program “learns” the new idle speed after adjustment.

This reference also explains the different types of General Motors IAC valves and contains a basic procedure to access the throttle stop adjusting screw on GM port and throttle-body injection systems. Each GM engine requires a specific procedure for minimum idle speed adjustment and idle learning. The complete instructions should be followed exactly for every engine. If the TPS is adjustable, check and readjust the TPS after adjusting minimum idle speed. Refer to Table G067-1 G067-1 below below for passenger car specifications, and to Table G067-2 G067-2 on page page G125 G125 for truck specifications. Table G067-1 G067-1 Passenger car minimum idle specifications (part 1 of 3)

En g i n e

1.6L 1.8L

Fu el Sy s t em

Minimum Idle Procedure

Idle Learn Procedure

Minimum Idle Specifications A/T

M/T

TBI

1988–93

6

B

1

450-550 P/ N

550-650

TBI

1982–86

O

A

1

675-725 P/N

775-825

PFI

1984–86

J

G

1

675-725 P/N

775-825

G

15

500-600 P/N

500-600

J

15

TBI 1.9L

Year

8th VIN Character

PFI MFI

1991–94 1995–2000

9 7 7 or 8

NA

* 1987–88 code W engines modified from MAF to speed-density systems use 1989 procedure. ** Do not set the minimum air rates on 3.3 N and 3.8 C, L, and 1 engines. Adjusting minimum air rates may cause other driveability complaints. complaints. The adjustment is set on a flow bench during manufacturing.

G122

G067

General Motor s Reference

Table G067-1 Passenger car minimum idle specifications (part 2 of 3)

Engine

8th VIN Character



1 or P

A

1

K

B

1

M

G

1

1988–89

1

B

1

1990–91

K

B

9

MFI

1992–94

H

NA

4

TBI

1990–93

G

B

9

MFI

1992–2000

4

NA

4

D or A

C

Fuel System

Year 1983–87

2.0L

2.2L

2.3L 2.4L 2.5L

TBI

PFI

1987–89

1987–89 1990–95

3

NA

5

MFI

1996–2000

T

NA

5

1982–86

R, U or 2

A

1

R or U

B

1990–94 1985–98 2.8L

3.0L

PFI

3.8L

9

B

550-650

NA 550-650 P/N

550-650

NA

7

NA NA** 475-525 P/N

750-800

550-650 P/N

550-650

450-550 P/N

550-650

500-600 D

600-700

PFI

1985–89

L

B

4

MFI

1997–2000

R

NA

5

NA (No Procedure)**

1988–94

T

D

1989–90

V

D

7

NA (Adjust to Air Counts)

1993–2000

M

1999–2000

J

NA

4

NA (No Procedure)**

1989–94

N

NA

8

NA (No Procedure)**

1991–97

X

D

7

NA (Adjust to Air Counts)

1993–95

S

SFI

1999–2000

E

NA

4

NA (No Procedure)**

SFI

1998–2000

H

NA

3

NA

PFI and SFI

1984–89

B, 3, 7 or 9

B

4

PFI

1988–95

C, L or 1

MFI

1995–2000

1 or K

NA

4

PFI MFI

1995 4.0L

550-650 P/N

D

MFI

3.5L

625-675

W*

3.1L

3.4L

1988

1 3

W* or 9

625-675 D

1989

PFI

3.3L

1987–89

S

M/T

8

1992–94

1987–89

A/T

5

MFI

TBI

Minimum Idle Specifications

SFI

1996–99

NA (Adjust to Air Counts) 450-550 D

450-550

450-550 D

450-550

NA (No Procedure)**

18 C

NA

2001

16

NA

17

* 1987–88 code W engines modified from MAF to speed-density systems use 1989 procedure. ** Do not set the minimum air rates on 3.3 N and 3.8 C, L, and 1 engines. Adjusting minimum air rates may cause other driveability complaints. The adjustment is set on a flow bench during manufacturing.

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G067


Table G067-1 Passenger car minimum idle specifications (part 3 of 3)

Engine

4.1L 4.3L

4.5L

Fuel System

Year

8th VIN Character


NA

450-550 P/N

NA

400-450 D

450-550

8

H

PFI

1987–88

7

I

TBI

1987–93

Z

F

14

PFI

1993–96

W

NA

14

DFI

1989

5

H

NA

PFI

1989–92

8

SFI

1990–93

5

I

11

4.9L

SFI CFI

1993–95

PFI

NA (No Procedure)** 450-550 P/N NA

12

9 or Y

NA

1991–95

B

I

11

500-550 P/N

NA

1982–83

7 or S

E

1

425-475

NA

450-550 D

450-550

400-450 P/N

400-450

1996–2000

1985 1896 1987–89

B F

F

1990–93

NA

3

4 2

NA

14

NA

TBI

1988–93

E

F

14

450-500 P/N

450-500

CFI

1982–84

8

E

1

475-525 D

475-525

400-450 P/N

450-500

400-450 D

450-500

425-475 P/N

450-500

450-500 P/N

450-500

1985 PFI

1986

B 8

TBI

PFI

1989

7

1989–95

J

1990–92

8

1992–97

P

1996

5

1997–2000

G

4

F

1987–89 5.7L

M/T

1982–88

SFI

Minimum Idle Specifications A/T

DFI

4.6L

5.0L


F 14 NA

NA

* 1987–88 code W engines modified from MAF to speed-density systems use 1989 procedure. ** Do not set the minimum air rates on 3.3 N and 3.8 C, L, and 1 engines. Adjusting minimum air rates may cause other driveability complaints. The adjustment is set on a flow bench during manufacturing.

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G067


Table G067-2 Truck minimum i dle specifications

Engine

Fuel System

Year

8th VIN Character



A

3

B

1

1985 2.5L

TBI

1986

E

1987–91 1986 2.8L

TBI

1987–89

TBI TBI

1990 1991–95 1986 1987–89

4.3L

PFI 1990

5.0L

TBI

R

5.7L

B

7.4L

TBI

1990

750-800

475-525 P/N

750-800

450-550 P/N

550-650

2

650-750 P/N

650-750

NA

14

550-650 P/N

NA

NA

3

400-450 D

Z*

2

425-525 D

Z**

B

Z or B*

400-500 D 10

Z or B** H or E

1987–89

750-800 p/n

Z

1990–95

1990–96

B

D

H

TBI

M/T

10

1987–89

1987–89

A/T

3

1990–93 3.1L

Minimum Idle Specifications

400-500

425-525 D 400-500 D

B

K†

2

400-450 D

10

475-525

2

K‡

B

K†

10

K‡ N

B

2 10

400-450 D 425-275 D 400-450 D

475-525

425-275 D 675-725 D

675-725

* All except S-10 models. ** S-10 only. † 8500 GVW or under. ‡ Over 8500 GVW.

Controlled Idle Speed (GM Late-models) GM has discontinued the use of minimum idle specification (Min Idle Spec) on some vehicles. The controlled idle speed specification (Controlled Idle Speed Spec) is used instead. This specification is not adjustable, it is used as a reference point to determine the condition of the engine and the IAC system. If rpm is out-of-range, then IAC counts or IAC position should be out-of-range. If air enters the intake somewhere other than the throttle plate or IAC passage (vacuum leak), or if the throttle plate screw is turned in too far, the IAC counts or IAC position is low and the rpm is high. If the throttle plates are coked, the IAC counts or IAC position may be too high. Minimum idle throttle plate position is factory-set and normally needs no adjustment. If the throttle plate screw has been adjusted, it should be reset.

z

To reset the throttle plate screw: 1.

Back the throttle plate screw out, until it no longer touches the throttle lever.

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G067


2.

Turn the screw in until it just touches the lever.

3. Turn the screw in one additional turn. 4. For all vehicles on Table G067-3, reset the controlled idle speed memory using Idle Learn Procedure 10 on page G136. Table G067-3 Controlled idle speed specifications for trucks, vans, and minivans (part 1 of 3)

Engine

Fuel System or Model

Year 1994–95

2.2L

MFI 1996–99

Transmission Type

Gear

Speed (RPM) IAC Counts1

M/T

N

950

5 to 20

A/T

D

800

15 to 40

M/T

N

A/T

D

NA

5 to 50

M/T

N

875

5 to 20

A/T

D

800

15 to 40

Loop Status 2

Closed

2.5L

All

1991–93

2.8L

All

1991–93

M/T

N

800

5 to 20

Open

3.4L

MFI

1996–99

A/T

D

NA

NA

NA

3.8L

MFI

1992–95

A/T

D

NA

NA

NA

D

600

5 to 30

N

550

2 to 20

N

675

3 to 30

A/T

D

600

5 to 30

M/T

N

700

A/T

D

650

M/T

N

675-725

A/T

D

575-625

M/T

N

650

15 to 50

A/T

D

600

5 to 40

M/T

N

525-575

A/T

D

565-615

M/T

N

675-725

A/T

D

575-625

1991–93

M/T

TBI 3

M/T 1991–95

TBI 4 4.3L

CPI, CMFI 3 C, K, G-Series

1996–99 1992–95

CPI, CMFI 3 S, T-Series

A/T

5

1996–97 1998–99

6

Closed

5 to 30 Varies

Closed

5 to 30 Varies

1. For 4.3L and all V8—Add 2 counts for engines with less than 500 miles, add 2 counts for every 1000 feet above sea level. For 2.5L and 2.8L—Add 1 count for every 1000 feet above sea level. 2. Allow engine to idle until proper fuel control status (open or closed loop) is reached. 3. Models under 8500 GVW. 4. Models over 8500 GVW. 5. 4.3L High-output M-Series van only. 6. 4.3L S and T-Series only. 7. C-10 with federal emissions, no secondary air (AIR)., and 3-speed automatic transmission only. 8. G-Series van and Suburban with a single catalytic converter only.

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G067


Table G067-3 Controlled idle speed specifications for trucks, vans, and minivans (part 2 of 3)

Engine


CPI, CMFI M-Van

3

Year 1996–97 1998–99

4.3L continued

CPI, CMFI L-Van

3

1996–97 1998–99

CPI 4 L, M, S, T-Series

1996–97 1998–99

4.8L

SFI C, K-Series TBI 4

1999

1991–95

5.0L

5.3L

CPI

1996–99

SFI C, K-Series

1999

TBI 3

1991–95 1991–95

5.7L

6.0L

TBI 4

1996–99

CPI

1996–99

SFI C, K-Series

1999

Transmission Type

Gear


M/T

N

525-575

A/T

D

565-615

M/T

N

675-725

A/T

D

575-625

M/T

N

525-575

A/T

D

565-615

A/T

D

625

M/T

N

675-725

A/T

D

625-675

M/T

N

675-725

A/T

D

625-675

M/T

N

A/T

D

M/T

N

625

A/T

D

525

A/T 7

D

525

M/T

N

A/T

D

M/T

N

A/T

D

M/T

N

625

A/T

D

525

M/T

N

600

M/T

N

600

A/T

D

550

M/T

N

650-700

A/T

D

525-575

M/T

N

A/T

D

NA

Loop Status 2

5 to 30 Varies 5 to 30

Closed

15 to 40 5 to 30 Varies Varies

5 to 30

Closed Open Closed

675-725

Varies

Closed

NA

Varies

Closed

NA

5 to 30

Open Closed Open

5 to 30

Closed

9

Closed Varies

Closed

Varies

Closed


G127

G067


Table G067-3 Controlled idle speed specifications for trucks, vans, and minivans (part 3 of 3)

Engine


Year 1991–93

TBI 7.4L

1994–95 MFI

1996–98

Transmission Type

Gear


M/T

N

800

A/T

D

750

M/T

N

725-775

A/T

D

650-700

M/T

N

700-750

A/T

D

575-650

Loop Status 2

Open 5 to 30 Closed Varies


General Motors IAC Valve Assemblies The IAC valve assemblies on GM throttle bodies are not all identical. Four different pintle shapes are used. In addition to the three shapes shown in Figure G067-1, a triple taper slope pintle is used. IAC valves also are identified as type 1, which has a collar at the end of the electrical connector, and type 2, which has no collar. The correct replacement part for a specific throttle body always must be installed.

Figure G067-1

Some IAC motor testers apply more voltage to the IAC motor than the normal ECM circuit applies. Such a tester makes a sluggish IAC motor appear to operate normally. An IAC count or IAC position of 2 or lower at idle may damage the IAC motor. This can be caused by a vacuum leak or incorrect idle speed. An IAC valve should not be disassembled and cleaned in solvent. Additionally, a used IAC valve should not be manually retracted in an attempt to adjust it because the internal threads may be damaged. New IAC valves can be adjusted manually. Some vehicles have an IAC control program that anticipates an increased engine load. For example, if the air conditioning is turned on, the ECM may increase IAC counts or IAC position to anticipate the load increase before the ECM engages the A/C compressor clutch. On speed density port fuel injection (PFI) systems (those using only a MAP sensor), you can save the IAC control memory by using the Scanner™ FIELD SERVICE functional test. Enter FIELD SERVICE with the engine running. Then disconnect the IAC connector and connect an

G128

G067


IAC tester to the IAC motor. Use the tester to check the circuit and control the IAC operation. The ECM retains the IAC control memory as long as the Scanner™ is in FIELD SERVICE. Reconnect the IAC with the Scanner™ in the FIELD SERVICE mode. You can test an IAC motor with an ohmmeter. Refer to a wiring diagram to identify the motor terminals. Disconnect the motor from the vehicle circuit and connect an ohmmeter across terminals A and B, then across C and D. Both readings should be 40 to 80 ohms. Motor resistance can be within specifications, but the motor may fail due to mechanical problems.

Throttle Stop Screw Adjustment Minimum idle speed is adjusted by the throttle stop screw in the throttle body. It is not adjusted by repositioning the IAC valve. The throttle bodies for both TBI systems and PFI systems have basically the same kind of throttle stop screw installation. The stop screw is located behind a concealment plug in the base of the throttle body. The plug is removed for access to the screw, which is usually done without removing the throttle body from the engine. The Buick 3800 V6 has a rubber cap or paint on the screw threads instead of a metal plug. Throttle bodies built before mid–1984 had a hardened steel plug over the screw that must be removed with a punch and a drill as shown in Figure G067-2. Throttle bodies built after mid-1984 have a soft plug that can be removed by piercing it with an awl or small punch and prying it out as shown in Figure G067-3. After the plug is removed, the throttle stop screw is adjusted similarly to an idle speed screw on a carburetor. GM recommends resealing the screw with RTV silicone sealant after adjustment to prevent tampering.

Figure G067-2

Figure G067-3

Minimum Idle Speed Procedures Check and adjust the minimum idle speed using the procedure listed in either Table G067-1, “Passenger car minimum idle specifications,” on page G122 or Table G067-2, “Truck minimum idle specifications,” on page G125.

i

NOTE: Always clean the throttle body before setting minimum idle. See Reference G008

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G067


Minim um Idle Speed Proc edure A 1.

Connect the Scanner™ to the vehicle for rpm readings and functional tests. Use ROAD TEST (C&D) or CODES & DATA AND ROAD TEST to avoid inaccurate rpm readings due to fixed timing.

2.

Start the engine and run it until it reaches normal operating temperature in closed loop. Allow idle rpm to stabilize.

3.

Disconnect the IAC valve motor connector with the engine running.

4.

Install an IAC passage plug tool (Thexton THX368 or equivalent) in the throttle body. Install the tool firmly to prevent air from leaking past the plug and creating a false minimum rpm reading.

5.

Check the minimum idle speed against the rpm specifications listed in Table G067-1 or Table G067-2. Adjust minimum idle speed, if necessary, using the throttle stop screw.

6.

After final adjustments, shut off the engine, remove the plug tool, and reconnect the IAC valve motor connector.

7.

After adjusting the idle speed, make sure TPS voltage is within specifications. Use the Scanner™ TPS CHECK & ADJUSTMENT SPECIFICATIONS functional test.

8.

Reset the learned idle memory, using the appropriate procedure 1 through 15.

Minim um Idle Speed Proc edure B 1.

Start the engine and run it until it reaches normal operating temperature in closed loop. Then turn the engine off.

2.

Connect the Scanner™ to the vehicle for rpm readings and functional tests.

3.

Turn the ignition on; do not start the engine.

4.

Select FIELD SERVICE on the Functional Tests menu and wait 45 seconds for the ECM to seat the IAC valve.

5.

Disconnect the IAC valve motor connector with the ignition still on and the Scanner™ in FIELD SERVICE mode.

6.

Select ROAD TEST (C&D) or ROAD TEST (NO C&D) from the Scanner™ Main Menu and start the engine. Connect a tachometer if ROAD TEST (C&D) is not available.

7.

Allow the idle rpm to stabilize, then check the minimum idle speed against the specifications in Table G067-1 or Table G067-2. Adjust minimum idle speed, if necessary, using the throttle stop screw.

8.

After final adjustments, shut off the engine and reconnect the IAC valve motor.

9.

After adjusting the idle speed, check the TPS voltage to make sure it is within specifications. Use the Scanner™ TPS CHECK & ADJUSTMENT SPECIFICATIONS functional test.

10. Reset the learned idle memory, using the appropriate procedure 1 through 15.

Minim um Idle Speed Proc edure C 1.

Connect the Scanner™ to the vehicle for IAC count readings and for functional tests.

2.


3.

Turn the throttle stop screw counterclockwise to back it out until a small gap is visible between the screw and the throttle lever.

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G067


4.

Turn the screw clockwise until it just contacts the throttle lever. Then, turn the screw an additional 1-1/2 turns

5.

Start the engine and select CODES & DATA AND ROAD TEST from the Main Menu.

6.

Check the IAC counts or IAC position at warm curb idle. They should be 5 to 45 in neutral.

7.


8.


Minim um Idle Speed Proc edure D 1.

Connect the Scanner™ to the vehicle for IAC count readings and for functional tests.

2.


3.

Turn the throttle stop screw counterclockwise to back it out until a small gap is visible between the screw and the throttle lever.

4.

Turn the screw clockwise until it just contacts the throttle lever. Then, turn the screw an additional 1-1/2 turns

5.

Start the engine and let the ECM reset the learned idle memory, following the appropriate procedure 1 through 15.

6.

Select CODES & DATA AND ROAD TEST from the Scanner™ Main Menu and check the IAC counts or IAC position at warm curb idle. The reading should be 10 to 20 in drive for an automatic transmission. If not within specifications, turn the throttle stop screw an additional 1/2 turn (maximum) in or out to obtain the proper IAC counts or IAC position.

7.


Minim um Idle Speed Proc edure E 1.


2.

Turn the ignition on and select ROAD TEST (NO C&D) from the Scanner™ Main Menu. Do not start the engine.

3.

Disconnect the IAC valve motor connectors at both throttle bodies with the engine off.

4.

Install the correct plug tool in the IAC passage of both throttle bodies. Be sure the tools are installed firmly so no air leaks past the plugs to create a false minimum rpm reading.

5.


6.

Install a water manometer (Kent-Moore Tool J23951 or equivalent) on the ported vacuum port of the rear throttle body.

7.

Adjust the rear throttle stop screw to get a manometer reading of about 6 inches of water.

8.

Remove the manometer from the rear throttle body and install it on the ported vacuum port of the front throttle body.

9.

If the manometer does not read approximately 6 inches of water, adjust the throttle balance screw to obtain the correct reading.

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G067


i

NOTE: The throttle balance screw is on the linkage, not in the throttle body, and it may be welded to the linkage. Cut the weld to make the adjustment. 10. Disconnect the manometer and reconnect vacuum lines as necessary. 11. Check the minimum idle speed against the rpm specifications in Table G067-1. Adjust minimum idle, if necessary, using the throttle stop screw on the rear throttle body. 12. After final adjustments, shut off the engine, remove the plug tools, and reconnect the IAC valve motor connectors. 13. After adjusting the idle speed, make sure TPS voltage tis within specifications. Use the Scanner™ TPS CHECK & ADJUSTMENT SPECIFICATIONS functional test. 14. Reset the learned idle memory, using the appropriate procedure 1 through 15.

Minim um Idle Speed Proc edure F 1.


2.

Start and run the engine until it reaches normal operating temperature and is in closed loop. Use the TPS CHECK & ADJUSTMENT SPECIFICATIONS on the Functional Tests menu to check TPS voltage. Be sure it is within limits; then turn the engine off.

3.

Turn the ignition on; do not restart the engine.

4.

Select FIELD SERVICE on the Functional Tests menu and wait 45 seconds for the ECM to seat the IAC valve.

5.

Disconnect the IAC valve motor connector with the ignition still on and the Scanner™ in FIELD SERVICE mode.

6.

Disconnect the set-timing connector. Refer to the vehicle emission control information (VECI) decal for directions.

7.

Select ROAD TEST (C&D) or ROAD TEST (NO C&D) from the Scanner™ Main Menu and start the engine.

8.

Allow idle rpm to stabilize, then check minimum idle speed against specifications in Table G067-1 or Table G067-2. Adjust minimum idle speed, if necessary, using the throttle stop screw.

9.

After final adjustments, shut off the engine and reconnect the IAC valve motor connector.

10. After adjusting the idle speed, make sure TPS voltage is still within specifications. 11. Reset the learned idle memory, using the appropriate procedure 1 through 15.

Minim um Idle Speed Proc edure G 1.


2.


3.

Disconnect the PCV hose to increase idle speed. This causes the ECM to seat the IAC valve in the throttle body air passage.

4.

Wait approximately 2 minutes, then disconnect the IAC valve motor connector with the engine running and the PCV hose disconnected.

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G067


5.

Reconnect the PCV hose and allow idle speed to stabilize at the minimum rpm.

6.

Check minimum idle speed against the rpm specifications in Table G067-1 or Table G067-2. Adjust minimum idle speed, if necessary, using the throttle stop screw.

7.

After final adjustments, shut off the engine and reconnect the IAC valve motor connector.

8.


9.


Minim um Idle Speed Proc edure H 1.

Start the engine and run it until it reaches normal operating temperature in closed loop. Allow idle rpm to stabilize and verify base ignition timing.

2.

Use Snap-on® tool THX399, or equivalent, to retract the idle speed control (ISC) motor until a gap exists between the ISC plunger and the throttle lever.

3.

Adjust the minimum idle speed to specifications, using the throttle body screw.

4.

After adjusting idle speed, make sure TPS voltage is within specifications (0.45v to 0.55v). Use the Scanner™ TPS CHECK & ADJUSTMENT SPECIFICATIONS functional test.

5.

For 1985–89 models, use tool number THX339, or equivalent, to extend the ISC motor to its maximum extension. Again, check the TPS voltage; it should be 0.95v to 1.10v. Turn the ISC plunger to adjust TPS voltage if necessary.

Minim um Idle Speed Proc edure I 1.

Before adjusting the idle speed, clean carbon or varnish deposits from the throttle body and throttle blade. Use a toothbrush or similar brush and GM top engine cleaner (part number 1052626) or AC-Delco tuneup conditioner (part number X66-P).

IMPORTANT: Do not use any solvent that contains methylethylketone to clean the throttle body. 2.

Start the engine and run it until it reaches normal operating temperature in closed loop. Allow idle rpm to stabilize and verify base ignition timing. Timing should be 10°btdc or 6°btdc if using regular unleaded gasoline.

3.

Ground the green “alternator-disable” lead to disable the alternator on Cadillac DeVille and Fleetwood while performing the rest of this procedure. (The ECM automatically disables the alternator on Eldorado and Seville during the ISC override.)

4.


5.

Adjust the minimum idle speed to specifications, using the throttle body screw.

6.

After adjusting idle speed, make sure TPS voltage is within specifications (0.45v to 0.55v). Use the Scanner™ TPS CHECK & ADJUSTMENT SPECIFICATIONS functional test.

7.

Use tool number THX339, or equivalent, to extend the ISC motor to its maximum extension. Again, check the TP sensor voltage; it should be: –

DeVille and Fleetwood—1.30v to 1.38v

–

Eldorado and Seville—1.15v to 1.20v

–

1987–88 Allante—0.22v to 1.32v

–

1989–92 Allante—use the Scanner™ or the vehicle Climate Control Driver Information Center (CCDIC) to read throttle angle, ranges from 13.4 to 15.8 degrees.

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8.

Turn the ISC plunger to adjust TP sensor voltage or throttle angle as necessary.

9.

Reset the learned idle memory and learned TPS memory, refer to Table G067-1.

Minim um Idle Speed Proc edure J 1.

Clean the throttle bore and blade, then run the engine until it is at operating temperature.

2.

Plug the IAC intake port with a suitable plug and expect the engine to either stall, or for the idle speed to decrease to 700 rpm or less.

3.

If idle speed does not drop to 700 rpm or less, look for a vacuum leak. Inspect the throttle body gasket, throttle shaft housing, PCV hose, PCV valve, and EGR mounting bolts.

Minim um Idle Speed Proc edure K 1.

Start the engine and run it until it reaches normal operating temperature in closed loop. Allow idle rpm to stabilize and verify base ignition timing.

2.


3.

Adjust the minimum idle speed to 375 rpm using the throttle body screw.

4.

Use the Scanner™ TPS CHECK & ADJUSTMENT SPECIFICATIONS functional test to verify that TPS voltage is within limits; 0.5v.

5.

Use Snap-on® tool THX399 to fully extend the plunger, engine speed should be 1500 rpm. Adjust plunger as needed. Then clear all codes.

Idle Learn Procedures Allow the ECM to reset the idle speed control memory using the appropriate procedure as listed inTable G067-1 on page G122 for cars or Table G067-2 on page G125 for trucks.

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NOTE: All trucks, vans, and minivans listed in Table G067-3 on page G126 use Procedure 10.

Idle Learn Pro cedure 1 Drive the vehicle at a steady 40 mph for 2 minutes with the engine warm and in closed loop. The ECM automatically resets the IAC valve position.

Idle Learn Pro cedure 2 1. Depress accelerator slightly. 2.

Start engine and run it at idle for 5 minutes.

3. Turn engine off for at least 10 seconds. 4.

Restart the engine and check for proper idle operation.

Idle Learn Pro cedure 3 Run the engine until it is at normal operating temperature and in closed loop. The ECM automatically resets the IAC valve position when the engine is turned off.

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Idle Learn Pro cedure 4 Turn the ignition on, then off. Do not start the engine. The IAC valve automatically resets.

Idle Learn Pro cedure 5 Drive the vehicle above 20 mph under moderate acceleration with the engine warm and in closed loop. The ECM automatically resets the IAC valve position.

Idle Learn Pro cedure 6 1.

Turn the air conditioning and all other accessories off.

2.

Start the engine and place the transmission in drive (automatic) or neutral (manual).

3.

Run the engine at idle until it reaches normal operating temperature in closed loop.

4.

Let the engine idle another 2 minutes at normal temperature in closed loop.


Turn the air conditioning and all other accessories off.

2.

Start the engine and put the transmission in drive for an automatic or neutral for a manual.

3.

Run the engine at idle until the cooling fan turns on, or a maximum of 10 minutes.

4.

Turn the ignition off for at least 5 seconds. Then repeat step 2.

5.

Let the engine idle for at least 5 minutes at normal temperature in closed loop.

Idle Learn Pro cedure 8 1. Turn the ignition on. 2.

Connect the Scanner™ and select FIELD SERVICE from the Functional Tests menu. Alternately, jump ALDL connector pin A to pin B for at least 5 seconds (Figure G067-4).

Figure G067-4

3.

Select ROAD TEST from the Scanner™ Main Menu, or remove the ALDL jump wire.

4.

Start the engine and check for proper idle control operation.


Start the engine and hold speed above 2000 rpm.

2.

Jump ALDL connector pin A to pin B (or use the Scanner™ FIELD SERVICE mode) for 10 seconds (Figure G067-4).

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G067


3.

Remove the jumper or exit FIELD SERVICE, release the throttle, and turn the engine off.

4. Restart the engine and check the idle speed.

Idle Learn Procedur e 10 1.

Turn the ignition on for 10 seconds. Do not start the engine.

2. Turn the ignition off for 10 seconds. 3.

Start the engine and verify the proper idle speed.


Start the engine and let it idle for 18 minutes.

2.

Apply the service brakes and shift the transmission to drive.

3.

Turn the air conditioning (climate control) off and idle the engine for at least 1 minute.

4.

Make sure the outside air temperature is at least 50°F.

5.

Turn the air conditioning (climate control) to AUTO and verify the A/C compressor clutch engages. Let the engine continue to idle for at least 1 minute.

6.

Shift the transmission to park and turn the ignition off.

7.

Continue with TPS learned memory adjustment as follows: a. Turn the ignition on. Do not start the engine. b. Enter on-board diagnostics. See Reference G074. c. Turn the ignition off for at least 20 seconds. Then turn the ignition on again. d. Reenter on-board diagnostics. e. Turn the ignition off again for at least 20 seconds. f. Turn ignition on again and repeat steps d and e one final time.

8.

Start the engine and verify correct idle speed and TPS voltage.

Idle Learn Procedur e 12

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NOTE: The outside air temperature must be over 50°F (10°C) for the compressor to turn on. 1. Start the engine. 2.

Run at idle until the coolant temperature is 176°F (80°C), then idle another 5 minutes.

3.

After 5-minutes, enter diagnostics (engine running).

4. Turn the ignition off. 5. Wait at least 20 seconds. 6. Turn the ignition on (engine not running). 7. Enter diagnostics. 8. Turn the ignition off. 9. Wait at least 20 seconds. 10. Turn the ignition on (engine not running). 11. Enter diagnostics. 12. Turn the ignition off. 13. Wait at least 20 seconds, then start the engine.

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14. Apply the brakes and place the transmission in drive range. 15. Turn the climate control center (CCC) off and allow the engine to idle 20 seconds. 16. Turn the CCC to AUTO and verify that the a/c compressor engages. Allow the engine to idle for another 20 seconds. 17. Place the transmission in park and turn the ignition off.

Idle Learn Procedur e 13 1. Turn the ignition on (engine not running). 2. Turn the ignition off. 3. Wait at least 20 seconds. 4. Turn the ignition on (engine not running). 5. Turn the ignition off. 6. Wait at least 20 seconds. 7. Turn the ignition on (engine not running). 8. Turn the ignition off. 9. Wait at least 20 seconds. 10. Start the engine. 11. Run at idle until the coolant temperature is 176°F (80°C), then idle another 5 minutes. 12. With the transmission in park, briefly accelerate the engine to over 1500 rpm. 13. Return to idle. 14. Apply the brakes and place the transmission in drive. 15. Idle the vehicle for 2 minutes, or until the MIL goes out.

Idle Learn Procedur e 14 1. Depress the accelerator slightly. 2.

Start the engine and tun it at idle for 5 seconds.

3.

Turn the engine off for at least 10 seconds.

4.



z Au tomatic Transmi ssio n: 1. Turn the ignition off. 2. Reconnect the battery to the PCM. 3. Turn off the A/C controls. 4.

Set the parking brake and block the drive wheels.

5. Start the engine. 6.

Run the engine until the engine coolant temperature reaches at least 176°F (80°C).

7. Shift the transmission into drive. 8. Allow the engine to idle for 5 minutes. 9. Shift the transmission into park. 10. Allow the engine to idle for 5 minutes.

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11. Turn the engine off for 30 seconds.

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Manual Transmission: 12. Turn the ignition off. 13. Reconnect the battery to the PCM. 14. Turn off the A/C controls. 15. Set the parking brake and block the drive wheels. 16. Place the transmission in neutral. 17. Start the engine. 18. Run the engine until the engine coolant temperature reaches at least 176°F (80°C). 19. Allow the engine to idle for 5 minutes. 20. Turn the engine off for 30 seconds.


Turn the ignition on, without starting the engine, and wait 30 seconds.

2. Turn the ignition off and wait 30 seconds. 3. Repeat steps 1 and 2.


Start the engine and allow to idle for15 seconds.

2. Turn the ignition off and wait 15 seconds. 3.



z

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TP Sensor Learn Procedure, perform f irst: 1.

Turn the ignition on, without starting the engine.

2.

Turn the ignition off and wait at least 20 seconds.

3.


4.


5.


6.


7.

Start the engine and perform the idle learn procedure.

Idle Learn Procedure: 1.

Start the engine, allow to warm up to 176°F (80°C), then run for 5 minutes.

2.

With the transmission in park, briefly accelerate to over 1500 rpm.

3. Return to idle. 4.

Apply the brakes and place transmission in drive.

5.

Run the engine at idle for 2 minutes, or until the MIL goes out. DO NOT TOUCH THE ACCELERATOR PEDAL.

6.

Clear codes.

G138

Ajuste IAC and TPS

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