GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide

Computerized Engine Systems

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OPERATION



See Figures 1 and 2

There are two types of computerized engine systems used on the vehicles covered in this information. The Computer Controlled Catalytic Converter System (C-4), installed on certain 1979 and all 1980 vehicles sold in California, is an electronically controlled exhaust emissions system. The Computer Command Control System (CCC), installed on all 1981 and later vehicles, is basically a modified version of the C-4 system.

The purpose of the C-4 system is to maintain the ideal air/fuel ratio at which the catalytic converter is most effective. Major components of the system include an Electronic Control Module (ECM), coolant temperature sensor, vacuum control switches, an oxygen sensor, an electronically controlled carburetor and a three-way oxidation reduction \catalytic converter. The system also includes a maintenance reminder flag connected to the odometer which becomes visible in the instrument cluster at regular intervals.

The ECM receives input signals from all sensors. It processes these signals and generates a control signal sent to the carburetor. The control signal cycles between on (lean command) and off (rich command). The amount of on and off time is a function of the input voltage sent to the ECM by the oxygen sensor.

A Check Engine Light is included in the C-4 System installation. When a fault develops, the light comes on, and a trouble code is set into the ECM memory. However, if the fault is intermittent, the light will go out, but the trouble code will remain in the ECM memory as long as the engine is running. The trouble codes are used as a diagnostic aid, and are pre-programmed.

Unless the required tools are available, troubleshooting the C-4 System should be confined to mechanical checks of electrical connectors, vacuum hoses and the like. All diagnosis and repair should be performed by a qualified mechanic with the proper diagnostic equipment.



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Fig. Fig. 1: C-4 system schematic

The CCC system's main advantage over its predecessor is that it can monitor and control a larger number of interrelated emission control systems.

This new system can monitor up to 15 engine/vehicle operating conditions and then use this information to control as many as 9 engine related systems. The system is thereby making constant adjustments to maintain good vehicle performance under all normal driving conditions while at the same time allowing the catalytic converter to effectively control the emissions of NOx, HC and CO.

The CCC system has some components in common with the C-4 system, although they are not interchangeable. These components include the Electronic Control Module (ECM), which, as previously stated, controls many more functions than does its predecessor, an oxygen sensor system, an electronically controlled variable mixture carburetor or throttle body fuel injection, a 3-way catalytic converter, throttle position and coolant sensors, a Barometric Pressure Sensor (BARO), a Manifold Absolute Pressure Sensor (MAP) and a Check Engine light in the instrument panel.

Components unique to the CCC system include the Air Injection Reaction (AIR) management system, a charcoal canister purge solenoid, EGR valve controls, a vehicle speed sensor (VSS), a transmission converter clutch solenoid (TCC), idle speed control and Electronic Spark Timing (EST).

In addition, the system has a built in diagnostic system that recognizes and identifies possible operational problems and alerts the driver through a Check Engine light in the instrument panel. The light will remain ON until the problem is corrected. The system also has built in back-up systems that in most cases of an operational problem, will allow for the continued operation of the vehicle in a near normal manner until the repairs can be made.



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Fig. Fig. 2: Common CCC system schematic

Not all engines use all components. Component applications may differ.

COMPONENT TESTING

Coolant Temperature Sensor

See Figure 3

The coolant sensor is a thermistor (a resistor which changes values based on temperature) mounted in the coolant stream. The ECM supplies a five volt signal to the coolant sensor through a resistor in the ECM and measures the voltage. The voltage will be high when the engine is cold and low when the engine is hot. By measuring the voltage, the ECM knows the coolant temperature which affects most systems the ECM controls. A failure in this circuit should set a trouble code 14 or 15. The sensor itself can be tested by removing the sensor (as outlined in Engine & Engine Overhaul ), then subjecting the sensor to changes in temperature and measuring the resistance at the terminals. This may be done with a water bath and a thermometer. Heat the water, watch the thermometer and measure the resistance across the terminals. Compare the readings to the chart. If the resistance values are out of range, replace the sensor.



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Fig. Fig. 3: Temperature to resistance values

Manifold Air Pressure (MAP) Sensor

See Figures 4, 5 and 6

The MAP sensor measures changes in the intake manifold pressure which result from engine load and speed changes, and converts this to a voltage output. MAP is the opposite of what you would read with a vacuum gauge. When manifold pressure is high, vacuum is low. The ECM uses the MAP sensor to control fuel delivery and ignition timing. A failure in this circuit should set a trouble code 34. To test the MAP sensor, have the ignition ON with the engine not running. Check voltage from sensor terminal B to A. It should be within the value specified in the chart. Apply 10 inches of vacuum to the sensor with a vacuum pump. There should be a 1.2-2.3 voltage change. If the sensor did not meet either of these requirements, have the system diagnosed and repaired by a qualified technician.



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Fig. Fig. 4: MAP sensor location on TBI engines



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Fig. Fig. 5: MAP sensor values (Non-Turbo)



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Fig. Fig. 6: MAP sensor values (Turbo)

VAC Sensor

See Figure 7

The differential pressure sensor is similar in appearance to the MAP and BARO sensors. However, it operates just the opposite of the MAP sensor in that it measures the difference between the manifold pressure and atmospheric pressure. The output of the sensor increases as the vacuum increases. A failure in this circuit should set a trouble code 34. To test this sensor, check vacuum at the sensor with a vacuum gauge. It should read at least 10 inches of vacuum. If it is not, repair before continuing. With the ignition ON and engine not running, check voltage from terminals B to A. It should be 0.50-0.64 volts. Connect a vacuum pump to the vacuum port on the sensor and apply 10 inches of vacuum. Voltage should be 2.25-2.95 volts and respond quickly. If the sensor did not meet either of these requirements, have the system diagnosed and repaired by a qualified technician.



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Fig. Fig. 7: VAC or MAP sensor location on carbureted engines

Barometric (BARO) Pressure Sensor

See Figures 8 and 9

The BARO sensor works like the MAP sensor, except that instead of measuring engine manifold pressure, it is open to the outside air, so it can measure barometric pressure. This allows the ECM to adjust for improved driveability at high altitudes. This sensor looks like the MAP sensor but it has a red insert in the harness connector cavity. A failure in the BARO circuit should set a trouble code 32. To test the BARO sensor, have the ignition ON with the engine not running. Check voltage from sensor terminal B to A. It should be within the value specified in the chart. Apply 10 inches of vacuum to the sensor with a vacuum pump. There should be a 1.2-2.3 voltage change. If the sensor did not meet either of these requirements, have the system diagnosed and repaired by a qualified technician.



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Fig. Fig. 8: BARO sensor location



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Fig. Fig. 9: BARO sensor values

Oxygen Sensor

See Figure 10

An oxygen sensor is used on all 1980 models built for California and on all 1981 and later models for all 50 states. The sensor protrudes into the exhaust stream and monitors the oxygen content of the exhaust gases. The difference between the oxygen content of the exhaust gases and that of the outside air generates a voltage signal to the ECM. The ECM monitors this voltage and, depending upon the value of the signal received, issues a command to adjust for a rich or a lean condition. A failure in the oxygen sensor circuit can cause trouble codes 13, 44 or 45. To test the oxygen sensor, connect a dwell meter on the 6 cylinder scale to the mixture control solenoid dwell terminal. Start and run the engine until it reaches normal operating temperature, then run the engine at fast idle for 1 minute.


CAUTION
Keep hands, hair, clothing, wires or any objects clear of moving engine parts.

Return the engine at idle and note dwell readings. It should be varying between 10 degrees and 50 degrees. If the sensor did not meet these requirements, have the system diagnosed and repaired by a qualified technician.



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Fig. Fig. 10: Oxygen sensor

Throttle Position Sensor

See Figures 11 and 12

On carbureted engines, the throttle position sensor is mounted in the carburetor body and is used to supply throttle position information in the ECM. The ECM memory stores an average of operating conditions with the ideal air/fuel ratios for each of those conditions. When the ECM receives a signal that indicates throttle position change, it immediately shifts to the last remembered set of operating conditions that resulted in an ideal air/fuel ratio control. The memory is continually being updated during normal operations. The TPS is used to regulate the mixture control solenoid, idle speed, EST and TCC lockup. To test the TPS on carbureted engines, first clear any stored codes as outlined in Trouble Codes later in this section. With the engine running at specified idle speed, have an assistant put the car in Drive while applying both the service and parking brakes. Stand to the side of the car and fully depress the TPS plunger for 15 seconds. Ground the diagnostic terminal and check for a trouble code 21. If this test did not set the code, have the system diagnosed and repaired by a qualified technician.



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Fig. Fig. 11: TPS on carbureted engines


CAUTION
Keep hands, hair, clothing, wires or any objects clear of moving engine parts.

On throttle body injection engines, the TPS is connected to the throttle shaft on the TBI unit. It is a potentiometer with one end connected to 5 volts from the ECM and the other to ground. A third wire is connected to the ECM to measure the voltage from the TPS. As throttle valve angle changes, so does the output of the TPS. On these engines, a failure in the TPS circuit should cause a trouble code 21 or 22. To test the TPS on TBI engines, have the ignition ON with the engine not running. Check voltage from sensor terminal B to A. It should be approximately 0.5 volts at idle and increase smoothly to about 5 volts at wide open throttle. If the sensor did not meet these requirements, have the system diagnosed and repaired by a qualified technician.



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Fig. Fig. 12: TPS on fuel injected engines

Idle Speed Control (ISC)

The idle speed control on carbureted engines does just what its name implies; it controls the idle. The ISC is used to maintain low engine speeds while at the same time preventing stalling due to engine load changes. The system consists of a motor assembly mounted on the carburetor which moves the throttle lever so as to open or close the throttle blades.

The whole operation is controlled by the ECM. The ECM monitors engine load to determine the proper idle speed. To prevent stalling, it monitors the air conditioning compressor switch, the transmission, the park/neutral switch and the ISC throttle switch. The ECM processes all this information and then uses it to control the ISC motor which in turn will vary the idle speed as necessary. To test the ISC motor operation, ground the diagnostic connector with the ignition ON, engine not running. The ISC should pulse smoothly in and out. If it did not meet these requirements, have the system diagnosed and repaired by a qualified technician.

Idle Air Control (IAC)

The purpose of the IAC valve on TBI engines, is to control idle speed, while preventing stalls due to engine engine load. The IAC valve mounted on the throttle body, controls idle by bypassing air around the throttle plates. If idle is too low, more air is bypassed around the plates to increase rpm. If it is too high, less air is bypassed to decrease rpm.

During idle, the proper position of the IAC valve is calculated by the ECM based on battery voltage, coolant temperature, engine load and engine rpm. To test IAC valve operation, have the engine idling at normal operating temperature in Park. Record idle speed.


CAUTION
Keep hands, hair, clothing, wires or any objects clear of moving engine parts.

Stop engine and disconnect the IAC valve, then restart the engine and recheck rpm. There should be an idle rpm increase. Stop the engine and reconnect the IAC valve, then restart the engine and recheck rpm once again. The idle should return to the original reading. If it did not meet these requirements, have the system diagnosed and repaired by a qualified technician.

Electronic Spark Timing (EST)

See Figure 13

All 1980 models with the 231 V6 engine and all 1981 and later models use EST. The EST distributor, as described in an earlier section, contains no vacuum or centrifugal advance mechanism and uses a seven terminal HEI module. It has four wires going to a four terminal connector in addition to the connectors normally found on HEI distributors. A reference pulse, indicating engine rpm is sent to the ECM. The ECM determines the proper spark advance for the engine operating conditions and then sends an EST pulse back to the distributor.

Under most normal operating conditions, the ECM will control the spark advance. However, under certain operating conditions such as cranking or when setting base timing, the distributor is capable of operating without ECM control. This condition is called BYPASS and is determined by the BYPASS lead which runs from the ECM to the distributor. When the BYPASS lead is at the proper voltage (5), the ECM will control the spark. If the lead is grounded or open circuited, the HEI module itself will control the spark. Disconnecting the 4-terminal EST connector will also cause the engine to operate in the BYPASS mode. To check EST performance, with the transmission in Park run the engine at fast idle and note timing change with a timing light as diagnostic lead is grounded.


CAUTION
Keep hands, hair, clothing, wires or any objects clear of moving engine parts.

If there is no change, stand to the side of the car and have an assistant in the car apply both the parking and service brakes. Perform the same test with the engine at idle in Drive as not all engines have EST operating when in Park. If there was no timing change in at least one of these tests, have the system diagnosed and repaired by a qualified technician.



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Fig. Fig. 13: EST circuitry schematic

Electronic Spark Control (ESC)

See Figures 14, 15 and 16

The Electronic Spark Control (ESC) system is a closed loop system that controls engine detonation by adjusting the spark timing. There are two basic components in this system, the module and the detonation sensor.

The module processes the sensor signal and modifies the EST signal to the distributor to adjust the spark timing. The process is continuous so that the presence of detonation is monitored and controlled. The module is not capable of memory storage.

The sensor is a magneto-restrictive device (meaning that is magnetically controls the flow of electricity), mounted in the engine block that detects the presence, or absence, and intensity of detonation according to the vibration characteristics of the engine. The output is an electrical signal which is sent to the controller. To test the ESC system, run the engine at fast idle and note RPM. Use a steel rod (eg. socket wrench breaker bar) to tap the front area of the intake manifold.



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Fig. Fig. 14: V6 knock sensor mounted on intake manifold



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Fig. Fig. 15: V8 knock sensor location


CAUTION
Keep hands, hair, clothing, wires or any objects clear of moving engine parts.

Tap the manifold rapidly with medium to heavy taps. Observe engine speed drop of 200 or more rpm. The engine should return to original rpm within 20 seconds after tapping stops. If the ESC system did not meet this requirement, have the system diagnosed and repaired by a qualified technician.



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Fig. Fig. 16: ESC module location

Transmission Converter Clutch (TCC)

See Figure 17

All 1981 and later models with an automatic transmission use TCC. The ECM controls the converter by means of a solenoid mounted in the transmission. When the vehicle speed reaches a certain level, the ECM energizes the solenoid and allows the torque converter to mechanically couple the transmission to the engine. When the operating conditions indicate that the transmission should operate as a normal fluid coupled transmission, the ECM will de-energize the solenoid. Depressing the brake will also return the transmission to normal automatic operation.

The TCC may lock up early and give a feeling of engine lugging or vibration if you install over-size tires on your vehicle. This is because the clutch engages at a certain vehicle speed, not at a certain engine rpm. You can usually install tires one size larger than the original equipment tires, but if they are two sizes or more larger than original equipment, you may experience this form of engine roughness. Testing of the TCC should be left to a qualified technician.



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Fig. Fig. 17: TCC solenoid

REMOVAL & INSTALLATION



Electronic Control Module (ECM)
  1. Disconnect the negative battery cable.
  2.  


WARNING
To prevent ECM damage, the ignition must always be OFF, BEFORE disconnecting the negative battery cable. The cable should be left disconnected when installing or removing the ECM. Before handling any electronic components, be sure to eliminate any possibility of electrostatic discharge by wearing a grounding strap attached to your wrist. Also, when replacing the PROM, it is possible to install it backwards. If it is installed backwards when the ignition key is turned ON, the PROM will be destroyed. Always note position of the PROM before removing it.

  1. Remove the right hand hush panel.
  2.  
  3. Disconnect the connectors to the ECM.
  4.  
  5. Remove the ECM.
  6.  
  7. If you are replacing the ECM, remove the PROM from the ECM and place it in the new ECM. Read the warning above.
  8.  
  9. Installation is the reverse of removal.
  10.  

Coolant Temperature Sensor
  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the senor electrical sensor.
  4.  

On most vehicles it will be necessary to drain the engine cooling system to a level just below the sensor, or the system will drain itself as the sensor is removed.

  1. Carefully back out the coolant sensor.
  2.  
  3. Installation is the reverse of removal.
  4.  

MAP, BARO, VAC Sensors
  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the electrical harness connection.
  4.  
  5. Disconnect the vacuum hose.
  6.  
  7. Remove the sensor from it's mounting bracket.
  8.  
  9. Installation is the reverse of removal.
  10.  

Oxygen Sensor

Take care when handling the oxygen sensor. The in-line connector and louvered end must be kept free of grease and other contaminants. Also, avoid using cleaning solvents of any type. Do not drop or roughly handle the oxygen sensor.

  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the sensor's electrical connection.
  4.  
  5. Carefully back out the oxygen sensor. The sensor may be hard to remove when the engine temperature is below 128°F (48°C). Excessive force may damage threads in the exhaust manifold or exhaust pipe. If removing sensor while the engine is warm, wear protection such as heavy gloves and long sleeves to prevent injury and burns.
  6.  

To install:
  1. Coat the threads of the oxygen sensor with anti-seize compound. Use only the special compound made for oxygen sensors.
  2.  
  3. Install sensor and torque to 30 ft. lbs. (41 Nm).
  4.  
  5. Connect the electrical connector.
  6.  
  7. Connect the negative battery cable.
  8.  

Throttle Position Sensor
CARBURETED ENGINES

See Figures 18, 19 and 20

Adjustment of the throttle position sensor is required after it's replacement. This requires the use expensive special tools. Review the procedures below before attempting replacement of the sensor.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner and vacuum hose.
  4.  
  5. Disconnect the idle speed control or idle speed solenoid electrical connections.
  6.  
  7. Remove the air horn:
    1. Attaching screws and remove the idle speed control, idle speed solenoid or idle load compensator.
    2.  
    3. Upper choke lever from the end of choke shaft by removing the retaining screw. Rotate upper choke lever to remove the choke rod from slot in lever.
    4.  
    5. Choke rod from the lower lever inside the float bowl casting. Remove rod by holding lower lever outward with a small screwdriver and twisting rod counterclockwise.
    6.  
    7. (E4ME) Remove the retainer from the pump link, and remove the link from the lever. DO NOT remove the pump lever from the air horn.
    8.  
    9. (E2ME) With tool J-25322 or a 3 / 32 in. (2.4mm) drift punch, drive roll pin (pump lever pivot pin) inward until end of pin is against air cleaner locating boss on air horn casting. Remove pump lever and lever from pump rod.
    10.  
    11. Front vacuum break hose from tube on float bowl.
    12.  
    13. Air horn-to-bowl screws; then remove the two countersunk attaching screws located next to the venturi. DO NOT drop the screws down the throttle bores.
    14.  
    15. Air horn from float bowl by lifting it straight up.

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      Fig. Fig. 18: Pump link lever (E4ME)

    16.  

  8.  
  9. Remove the solenoid-metering rod plunger by lifting it straight up.
  10.  
  11. Remove the air horn gasket by lifting it from the dowel locating pins on the float bowl. DISCARD GASKET.
  12.  
  13. Remove the staking holding the TPS in bowl as follows:
    1. Lay a flat tool or metal piece across the bowl casting to protect the gasket sealing surface.
    2.  
    3. Use a small screwdriver to depress TPS sensor lightly and hold against spring tension.
    4.  
    5. Carefully pry upward with a small chisel or equivalent to remove bowl staking, make sure prying force is exerted against the metal piece and not against the bowl casting.
    6.  
    7. Push up from bottom on electrical connector and remove TPS and connector assembly from bowl.
    8.  

  14.  

To install:
  1. Align and install TPS and connector assembly with aligning groove in bowl casting. Push down on connector and sensor assembly so that connector and wires are located below the bowl surface. Be sure the green TPS actuator is in place in the air horn.
  2.  
  3. Install air horn, holding down on pump plunger assembly against return spring tension, and aligning holes in gasket over TPS plunger, solenoid plunger return spring, metering rods, solenoid attaching screw and electrical connector. Position gasket over the two dowel locating pins on the float bowl.
  4.  
  5. Install solenoid-metering rod plunger, holding down on air horn gasket and pump plunger assembly, and aligning slot in end of plunger with solenoid attaching screw.
  6.  
  7. Carefully lower air horn assembly onto float bowl while positioning the TPS adjustment lever over the TPS, and guiding pump plunger stem through seal in air horn casting. To ease installation, insert a thin screwdriver between air horn gasket and float bowl to raise the TPS adjustment lever positioning it over the TPS.
  8.  
  9. Install air horn attaching screws. Tighten all screws evenly and securely, following the air horn tightening sequence. Don't forget the countersunk screws in the venturi area.
  10.  
  11. Install the front vacuum break and bracket assembly on the air horn, using two attaching screws and tighten securely.
  12.  
  13. (E4ME) Re-install pump rod into hole in pump lever and insert retainer pin. (E2ME) Hook upper end of pump rod into hole in pump lever and place lever between raised bosses on air horn casting, making sure lever engages TPS actuator plunger and the pump plunger stem. Align hole in pump lever in holes in air horn casting bosses. Using a small drift or rod to diameter of the pump lever roll pin will aid alignment. Using sidecutting pliers on the end of the roll pin, pry the roll pin only enough to insert a thin blade screwdriver between the end of the pump lever roll pin and the air cleaner locating boss on the air horn casting. Use screwdriver to push pump lever roll pin back through the casting until the end of the pin is flush with the casting bosses in the air horn.
  14.  

Use care installing the roll pin to prevent damage to the pump lever bearing surface and casting bosses.

  1. Install the choke rod into the lower choke lever inside the bowl cavity. Install choke rod in slot in upper choke lever, and position lever on end of choke shaft, making sure the flats on the end of the shaft align with the flats in the lever. Install attaching screw and tighten securely. When properly installed, the lever will point to the rear of the carburetor and the number on the lever will face outward.
  2.  
  3. Install idle speed control motor.
  4.  
  5. Reconnect all electrical connections
  6.  
  7. Reconnect negative battery cable.
  8.  

To adjust:

To adjust the TPS it is necessary to remove the plug covering the TPS adjusting screw first.

  1. Using a 5 / 16 in. (2mm) drill, drill a 1 / 8 in. deep hole in the aluminum plug covering the TPS adjustment screw. Use care in drilling to prevent damage to the adjustment screw head.
  2.  



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Fig. Fig. 19: Removing adjustment screw plug

  1. Start a No. 8 1 / 2 in. long self-tapping screw in the drilled hole turning screw in only enough to ensure good thread engagement in hole.
  2.  
  3. Placing a wide-blade screwdriver between screw head and air horn casting, pry against screw heads and remove plug. DISCARD PLUG.
  4.  
  5. Adjustment is required if voltage reads different than 0.31 volts on the E2ME or 0.40 volts on the E4ME, by more than plus or minus0.05 volts. If it is within these specifications, no adjustment is needed.
  6.  
  7. Using Tool J-28696, remove TPS adjustment screw.
  8.  



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Fig. Fig. 20: Adjusting TPS

  1. Connect a digital voltmeter from TPS center terminal "'B" to bottom terminal "C".
  2.  
  3. With ignition ON, engine not running, reinstall TPS adjustment screw and with Tool J-28696, BT-7967A quickly adjust screw to obtain 0.48 volts with the A/C off and throttle in curb idle position.
  4.  
  5. After adjustment, install new plug in air horn, driving plug into place until flush with raised boss on casting.
  6.  

TBI ENGINES

To remove the TPS on these engines, disconnect the electrical connector and remove the two attaching screws. Make sure throttle is in normal closed idle position then install the TPS on the TBI assembly. With the TPS lever located ABOVE the tang on the actuator lever, install the attaching screws using a thread locking compound. Reconnect electrical connector. No adjustment is necessary.

ISC Motor
  1. Disconnect the electrical connector with the ignition OFF.
  2.  
  3. Remove the ISC motor and bracket.
  4.  
  5. Installation is the reverse of removal. Refer to Engine Electrical for adjustment.
  6.  

IAC Valve

See Figure 21

  1. Remove the air cleaner.
  2.  
  3. Disconnect the electrical connector.
  4.  
  5. Remove the valve using a 1 1 / 4 (32mm) wrench on the hex surface only.
  6.  


WARNING
Before installing a new IAC valve, measure the distance that the valve is extended. If the cone is extended too far, damage may occur to the valve when installed.

To install:
  1. Measure from motor housing to end of cone. Distance should be no more than 1 1 / 8 in (28mm).
  2.  
  3. If necessary distance can be reduced as follows. Identify valve as being Type 1 or Type 2. For Type 1 valves, exert firm pressure on valve to retract it (a slight side-to-side movement may be helpful). For Type 2 valves, compress the retainer spring while turning valve in with a clockwise motion. Return spring to original position with straight portion of the spring end aligned with the flat surface of the valve.
  4.  



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Fig. Fig. 21: Identifying Type 1 or 2 IAC valve

  1. Install the new valve and gasket to the throttle body. Tighten the valve to 13 ft. lbs. (18 Nm).
  2.  
  3. Reconnect the electrical connector and reinstall the air cleaner.
  4.  
  5. Start the engine and allow it to reach operating temperature.
  6.  
  7. The ECM will reset idle speed when vehicle is driven above 35 mph (56 kph).
  8.  

Electronic Spark Timing System

Refer to Engine Electrical for module removal and installation.

Electronic Spark Control System
  1. To remove the ESC Knock Sensor, disconnect the negative battery cable and the sensor connector.
  2.  
  3. Remove the sensor from the engine block
  4.  
  5. To install the sensor, first apply a sealer such as soft tape to the threads then install sensor.
  6.  
  7. Reconnect the sensor connector and battery cable.
  8.  
  9. To remove the ESC Module, disconnect the electrical connector and the attaching screws.
  10.  
  11. Remove the ESC Module.
  12.  
  13. Installation is the reverse of removal.
  14.  

Torque Converter Clutch

For TCC removal procedures refer to Drive Train .

 
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