GM Prizm/Nova 1985-1993 Repair Guide

CHECKING AND ADJUSTMENT

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1985-88 VIN Code 4 Carbureted Engine

See Figure 1

This engine requires a special tachometer hook-up to the service connector wire coming out of the distributor. As many tachometers are not compatible with this hook-up, we recommend that you consult with the manufacturer or salesman before purchasing a certain type.


WARNING
NEVER allow the ignition coil terminal to become grounded; severe and expensive damage can occur to the coil and/or igniter!

  1. Warm the engine to normal operating temperature. Do not attempt to check timing or idle on a cold engine - all the readings will be different. Connect a tachometer and check the engine idle speed to be sure it is within the specification given in the Tune-Up Specifications chart at the beginning of this Section. Adjust the idle if needed and shut the engine off.
  2.  
  3. If the timing marks are difficult to see, use a dab of paint or chalk to make them more visible.
  4.  



Click image to see an enlarged view

Fig. Fig. 1: Ignition timing adjustment and mark location, 1985-88 VIN Code 4 carbureted Nova

  1. Connect a timing light according to the manufacturer's instructions.
  2.  
  3. Label and disconnect the vacuum line(s) from the distributor vacuum unit. Plug it (them) with a pencil or golf tee(s).
  4.  
  5. Be sure that the timing light wires are clear of the fan and start the engine.
  6.  
  7. Allow the engine to run at the specified idle speed with the gearshift in Neutral.
  8.  


CAUTION
Be sure that the parking brake is set and the wheels are blocked to prevent the car from rolling in either direction.

  1. Point the timing light at the marks on the tab alongside the crank pulley. With the engine at idle, timing should be at the specification given on the Tune-Up Specification Chart at the beginning of the section.
  2.  
  3. If the timing is not at the specification, loosen the bolts at the base of the distributor just enough so that the distributor can be turned. Turn the distributor to advance or retard the timing as required. Once the proper marks are seen to align with the timing light, timing is correct.
  4.  
  5. Stop the engine and tighten the bolts. Start the engine and recheck the timing. Stop the engine; disconnect the tachometer and the timing light. Connect the vacuum line(s) to the distributor vacuum unit.
  6.  

1988 VIN Code 5 Engine - Fuel Injected Nova

See Figures 2 and 3

This engine requires a special tachometer hook-up to the service connector wire coming out of the distributor. As many tachometers are not compatible with this hook-up, we recommend that you consult with the manufacturer or salesman before purchasing a certain type.


WARNING
NEVER allow the ignition coil terminal to become grounded; severe and expensive damage can occur to the coil and/or igniter.

  1. Warm the engine to normal operating temperature. Do not attempt to check timing or idle on a cold engine - all the readings will be different.
  2.  
  3. Using a small jumper wire, short both terminals of the Check Engine connector located near the wiper motor.
  4.  



Click image to see an enlarged view

Fig. Fig. 2: Jumper wire must be installed to check the timing on fuel injected Novas, 1988 VIN Code 5 engines

  1. Connect a tachometer and check the engine idle speed to be sure it is within the specification given in the Tune-Up Specifications chart at the beginning of this section. Adjust the idle if needed and shut the engine OFF.
  2.  
  3. If the timing marks are difficult to see, use a dab of paint or chalk to make them more visible.
  4.  
  5. Connect a timing light according to the manufacturer's instructions.
  6.  
  7. Start the engine and use the timing light to observe the timing marks. With the jumper wire in the connector the timing should be 10° BTDC with the engine fully warmed up and the transmission in Neutral. If the timing is not correct, loosen the bolts at the distributor just enough so that the distributor can be turned. Turn the distributor to advance or retard the timing as required. Once the proper marks are seen to align with the timing light, timing is correct.
  8.  



Click image to see an enlarged view

Fig. Fig. 3: Ignition timing marks on the 1988 VIN Code 5 and all 1991-93 engines. Note the small notch on the pulley; this is the mark to align with the degree scale

  1. Without changing the position of the distributor, tighten the distributor bolts and double check the timing with the light.
  2.  
  3. Disconnect the jumper wire at the Check Engine connector.
  4.  
  5. Check the timing again with the light. Manual transmission cars should now show timing in excess of 16° BTDC and automatic transmission cars more than 12° BTDC. If necessary, repeat the timing adjustment procedure.
  6.  
  7. Shut the engine OFF and disconnect all test equipment.
  8.  

1989-92 VIN Code 6 Engine - Fuel Injected Prizm

See Figures 3, 4, 5 and 6

This engine requires a special tachometer hook-up to the service connector port on the left shock tower. As many tachometers are not compatible with this hook-up, we recommend that you consult with the manufacturer or salesman before purchasing a certain type.


WARNING
NEVER allow the tachometer terminal to become grounded; severe and expensive damage can occur to the coil and/or igniter.

  1. Warm the engine to normal operating temperature. Turn all electrical accessories OFF.
  2.  
  3. Connect a tachometer and check the engine idle speed to be sure it is within the specification given in the Tune-Up Specifications chart at the beginning of this section. Adjust the idle if needed and shut the engine OFF.
  4.  



Click image to see an enlarged view

Fig. Fig. 4: Checking the timing requires shorting the E1 and T terminals at the diagnostic connector, 1989-92 VIN Code 6 and 1990 VIN Code 5 engines - see text for details

  1. Connect a timing light according to the manufacturer's instructions.
  2.  
  3. Remove the cap on the diagnostic connector. Using a small jumper wire, short terminals E1 and T together.
  4.  
  5. Start the engine and use the timing light to observe the timing marks. With the jumper wire in the connector, the timing should be at the specification listed on the Vehicle Emissions Label located under the hood. If the timing is not correct, loosen the bolts at the distributor just enough so that the distributor can be turned. Turn the distributor to advance or retard the timing as required. Once the proper marks are seen to align with the timing light, timing is correct.
  6.  
  7. Without changing the position of the distributor, tighten the distributor bolts to 14 ft. lbs. and double check the timing with the light.
  8.  
  9. Remove the jumper wire from the diagnostic connector and reinstall the cap.
  10.  
  11. On 1989-90 VIN code 6 engines, disconnect the air control valve (ACV) connector at the intake manifold.
  12.  



Click image to see an enlarged view

Fig. Fig. 5: Correct tachometer hook-up - 1989-92 Prizm



Click image to see an enlarged view

Fig. Fig. 6: Use care when handling the air control valve wiring. The connector has a locking device which must be released before removal

  1. Recheck the timing; it should be 10° BTDC.
  2.  
  3. On 1989-90 VIN code 6 engines, reconnect the ACV connector.
  4.  
  5. Shut the engine OFF and disconnect all test equipment.
  6.  

1991-92 VIN Code 5 and All 1993 Engines

See Figures 3, 4, 5, 6 and 7

This engine requires a special tachometer hook-up to the service connector port on the left shock tower. As many tachometers are not compatible with this hook-up, we recommend that you consult with the manufacturer or salesman before purchasing a certain type.


WARNING
NEVER allow the tachometer terminal to become grounded; severe and expensive damage can occur to the coil and/or igniter.

  1. Warm the engine to normal operating temperature. Turn all electrical accessories OFF.
  2.  
  3. Connect a tachometer and check the engine idle speed to be sure it is within the specification given in the Tune-Up Specifications chart at the beginning of this section. Adjust the idle if needed and shut the engine OFF.
  4.  



Click image to see an enlarged view

Fig. Fig. 7: Checking the timing requires shorting the E1 and TE1 terminals at the diagnostic connector, 1991-92 VIN Code 5 and all 1993 engines - see text for details

  1. Connect a timing light according to the manufacturer's instructions.
  2.  
  3. Remove the cap on the diagnostic connector. Using a fused jumper wire, connect terminals E1 and TE1 together.
  4.  
  5. Start the engine and use the timing light to observe the timing marks. With the jumper wire in the connector, the timing should be at the specification listed on the Vehicle Emissions Label located under the hood. If the timing is not correct, loosen the bolts at the distributor just enough so that the distributor can be turned. Turn the distributor to advance or retard the timing as required. Once the proper marks are seen to align with the timing light, timing is correct.
  6.  
  7. Without changing the position of the distributor, tighten the distributor bolts to 14 ft. lbs. and double check the timing with the light.
  8.  
  9. Remove the jumper wire from the diagnostic connector and reinstall the cap.
  10.  
  11. Shut the engine OFF and disconnect all test equipment.
  12.  

 
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