Toyota Cressida and Van 1983-1990

Ignition Timing

Print

DESCRIPTION



Ignition timing is the measurement in degrees of crankshaft rotation of the instant the spark plugs in the cylinders fire, in relation to the location of the piston, while the piston is on its compression stroke.

Ignition timing is adjusted by loosening the distributor locking device and turning the distributor in the engine.

Ideally, the air/fuel mixture in the cylinder will be ignited (by the spark plug) and just beginning its rapid expansion as the piston passes top dead center (TDC) of the compression stroke. If this happens, the piston will be beginning the power stroke just as the compressed (by the movement of the piston) and ignited (by the spark plug) air/fuel mixture starts to expand. The expansion of the air/fuel mixture will then force the piston down on the power stroke and turn the crankshaft.

It takes a fraction of a second for the spark from the plug to completely ignite the mixture in the cylinder. Because of this, the spark plug must fire before the piston reaches TDC, if the mixture is to be completely ignited as the piston passes TDC. This measurement is given in degrees of top dead center (BTDC). If the ignition timing setting for your engine is seven degrees (7°) BTDC, this means that the spark plug must fire at a time when the piston for that cylinder is 7° before top dead center of the compression stroke. However, this only holds true while your engine is at idle speed.

As you accelerate from idle, the speed of your engine (rpm) increases. The increase in rpm means that the pistons are now traveling up and down much faster. Because of this, the spark plugs will have to fire even sooner if the mixture is to be completely ignited as the piston passes TDC. To accomplish this, the distributor incorporates means to advance the timing of the spark as engine speed increases.

The distributor in your Toyota has two means of advancing the ignition timing. One is called centrifugal advance and is actuated by weights in the distributor. The other advance system is controlled by that on board computer in your vehicle.

The 1984-85 Van models, use a vacuum advance diaphragm that is located on the side of the distributor. Because this mechanism changes the ignition timing, it is necessary to disconnect and plug the one or two vacuum lines from the vacuum advance unit when setting the basic ignition timing.

If ignition timing is set too far advanced (BTDC), the ignition and expansion of the air/fuel mixture in the cylinder will try to force the piston down the cylinder while it is still traveling upward. This causes engine ping, a sound which resembles marbles being dropped into an empty tin can. If the ignition timing is too far retarded (after, or ATDC), the piston will have already started down on the power stroke when the air/fuel mixture ignites and expands. This will cause the piston to be forced down only a portion of its travel and will result in poor engine performance and lack of power.

Ignition timing adjustment is checked with a timing light. This instrument is connected to the number one (No. 1) spark plug of the engine. The timing light flashes every time an electrical current is sent from the distributor, through the No. 1 spark plug wire, to the spark plug. The crankshaft pulley and the front cover of the engine are marked with a timing pointer and a timing scale. When the timing pointer is aligned with the 0 mark on the timing scale, the piston in No. 1 cylinder is at TDC of its compression stroke. With the engine running, and the timing light aimed at the timing pointer and timing scale, the stroboscopic flashes from the timing light will allow you to check the ignition timing setting of the engine. The timing light flashes every time the spark plug in the No. 1 cylinder of the engine fires. Since the flash from the timing light makes the crankshaft pulley seem stationary for a moment, you will be able to read the exact position of the piston in the No. 1 cylinder on the timing scale on the front of the engine.

INSPECTION & ADJUSTMENT



1983-88 Cressida


Click image to see an enlarged view

Fig. Fig. 1 Short the terminals of the check engine connector to check the timing-1983-84 Cressida



Click image to see an enlarged view

Fig. Fig. 2 Attach a tachometer to the service connector as shown



Click image to see an enlarged view

Fig. Fig. 3 Aim the timing light on the timing marks on the pulley



Click image to see an enlarged view

Fig. Fig. 4 Short these two terminals of the check engine connector on 1985-88 Cressida models

  1. Warm up the engine. Connect a tachometer and check the engine idle speed to be sure that it is within the specification given in the Tune-Up Specifications chart at the beginning of the section.
  2.  

As some tachometers are not compatible with this ignition system, we recommend that you confirm the compatibility of your tachometer before using. Never allow the ignition coil terminals to touch ground as it could result in damage to the igniter and/or the ignition coil. Do not disconnect the battery cables while the engine is running. Make sure that the igniter is properly grounded to the body. When a tachometer is connected to the vehicle, always connect the positive terminal of the tachometer to the engine service connector located under in the engine compartment.

  1. If the timing marks are difficult to see, clean them off using a suitable solvent and use a dab of paint or chalk to make them more visible.
  2.  
  3. Using a suitable piece of jumper wire short the terminals of the check engine connector (T and E 1 ), located in the engine compartment.
  4.  
  5. Connect a timing light according to the manufacturer's instructions. If the timing light being used is a non-inductive type light that has three wires, one (usually blue or green) must be installed with an adapter between the No. 1 spark plug lead and the spark plug. The other leads are connected to the positive (+) battery terminal (usually a red lead) and the other to the negative (-) battery terminal (usually a black lead).
  6.  
  7. If the timing light is an inductive type light, connect the inductive clamp around the number one spark plug wire and the other 2 cables to the positive and negative post of the battery.
  8.  
  9. Be sure that the timing light wires are clear of the fan and start the engine.
  10.  


CAUTION
Keep fingers, clothes, tools, hair, and leads clear of the spinning engine fan. Be sure that you are running the engine in a well ventilated area.

  1. Allow the engine to run at the specified idle speed with the gearshift in Neutral with manual transmission and Drive (D) with automatic transmission.
  2.  


CAUTION
Be sure that the parking brake is set and that the front wheels are blocked to prevent the car from rolling forward, especially when Drive is selected with an automatic.

  1. Point the timing marks at the timing marks that are on the engine. With the engine at idle, the timing should be at 10° before top dead center (BTDC).
  2.  
  3. If the timing is not at the specification, loosen the pinch bolt 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 pinch bolt. Start the engine and recheck timing and the idle speed, adjust as necessary. Stop the engine. Disconnect the tachometer, jumper wire and timing light.
  6.  

1989-90 Cressida


Click image to see an enlarged view

Fig. Fig. 5 Short these terminals of the check engine connector located on the strut tower-1989-90 Cressida



Click image to see an enlarged view

Fig. Fig. 6 Attaching a tachometer to the service connector-1989-90 Cressida



Click image to see an enlarged view

Fig. Fig. 7 Aim the timing light on the timing marks-1989-90 Cressida shown

  1. Warm up the engine. Connect a tachometer and check the engine idle speed to be sure that it is within the specification given in the Tune-Up Specifications chart at the beginning of the section.
  2.  

As some tachometers are not compatible with this ignition system, we recommend that you confirm the compatibility of your tachometer before using. Never allow the ignition coil terminals to touch ground as it could result in damage to the igniter and/or the ignition coil. Do not disconnect the battery cables while the engine is running. Make sure that the igniter is properly grounded to the body. When a tachometer is connected to the vehicle, always connect the positive terminal of the tachometer to the ignition (IG) terminal of the engine service connector located under in the engine compartment.

  1. If the timing marks are difficult to see, clean them off using a suitable solvent and use a dab of paint or chalk to make them more visible.
  2.  
  3. Using a suitable piece of jumper wire short the terminals of the check engine connector (TE 1 and E 1 ), located in the engine compartment.
  4.  
  5. Connect a timing light according to the manufacturer's instructions.
  6.  
  7. Be sure that the timing light wires are clear of the fan and start the engine.
  8.  
  9. Allow the engine to run at the specified idle speed with the gearshift in Neutral with manual transmission and Drive (D) with automatic transmission.
  10.  
  11. Point the timing marks at the timing marks that are on the engine. With the engine at idle, the timing should be at 10° before top dead center (BTDC).
  12.  
  13. If the timing is not at the specification, loosen the pinch bolt 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.
  14.  
  15. Stop the engine and tighten the pinch bolt. Start the engine and recheck timing and the idle speed, adjust as necessary. Stop the engine. Disconnect the tachometer, jumper wire and timing light.
  16.  

With the jumper wire removed from the engine check connector, the ignition timing advance will be between 9-11° BTDC.

Van


Click image to see an enlarged view

Fig. Fig. 8 Shorting the terminals of the check engine connector-3Y-EC and 4Y-EC engines



Click image to see an enlarged view

Fig. Fig. 9 Attaching a tachometer to the service connector-Van



Click image to see an enlarged view

Fig. Fig. 10 Disconnect the vacuum line at the advance unit and plug it-1984-85 Van



Click image to see an enlarged view

Fig. Fig. 11 The timing mark location on the 4Y-EC Van engine



Click image to see an enlarged view

Fig. Fig. 12 Timing mark graduations-Van



Click image to see an enlarged view

Fig. Fig. 13 Using a wrench, set the No. 1 cylinder to TDC of the compression stroke

  1. Warm up the engine. Connect a tachometer and check the engine idle speed to be sure that it is within the specification given in the Tune-Up Specifications chart at the beginning of the section.
  2.  

As some tachometers are not compatible with this ignition system, we recommend that you confirm the compatibility of your tachometer before using. Never allow the ignition coil terminals to touch ground as it could result in damage to the igniter and/or the ignition coil. Do not disconnect the battery cables while the engine is running. Make sure that the igniter is properly grounded to the body. When a tachometer is connected to the vehicle, always connect the positive terminal of the tachometer to the engine service connector located on or near the distributor assembly in the engine compartment.

  1. If the timing marks are difficult to see, clean them off using a suitable solvent and use a dab of paint or chalk to make them more visible.
  2.  
  3. On the 1984-85 Van models, disconnect and plug the vacuum lines at the vacuum advance unit on the side of the distributor. On the 1986-89 van models, use a suitable piece of jumper wire to short the terminals of the check engine connector, located in the engine compartment.
  4.  
  5. Connect a timing light according to the manufacturer's instructions.
  6.  
  7. Be sure that the timing light wires are clear of the fan and start the engine.
  8.  


CAUTION
Keep fingers, clothes, tools, hair, and leads clear of the spinning engine fan. Be sure that you are running the engine in a well ventilated area.

  1. Allow the engine to run at the specified idle speed with the gearshift in Neutral with manual transmission and Drive (D) with automatic transmission.
  2.  


CAUTION
Be sure that the parking brake is set and that the front wheels are blocked to prevent the car from rolling forward, especially when Drive is selected with an automatic.

  1. Point the timing marks at the timing marks that are on the engine. With the engine at idle, the timing should be at:

    1984-85 models, 8° before top dead center (BTDC) at idle
     
    1986-89 models, 12° before top dead center (BTDC) at idle
     

  2.  
  3. If the timing is not at the specification, loosen the pinch bolt 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 pinch bolt. Start the engine and recheck timing and the idle speed, adjust as necessary. Stop the engine. Disconnect the tachometer, jumper wire and timing light. Reconnect the vacuum lines on the advance diaphragm.
  6.  

 
label.common.footer.alt.autozoneLogo