Toyota Pick-ups/Land Cruiser/4Runner 1989-1996

Ignition Timing

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GENERAL INFORMATION



Ignition timing is the measurement in degrees of crankshaft rotation at the instant the spark plug fires while the piston is on its compression stroke.

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

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 air/fuel mixture starts to burn and expand. The expansion (explosion) 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 crankshaft rotation before the piston reaches top dead center (BTDC). If the ignition timing setting for your engine is seven (7°) BTDC, this means that the spark plug must fire at the time when the piston for that cylinder is 7° before reaching the top of its compression stroke. However, this only holds true while your engine is at idle speed.

As the engine accelerates from idle, the speed of the engine (rpm, or revolutions per minute) 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 at least two means of advancing the ignition timing. One is called centrifugal advance and is actuated by weights in the distributor. The other is called vacuum advance and is controlled by that larger circular housing on the side of the distributor. In many later models, the vacuum advance is replaced by full computerized control, thanks to the Engine Control Unit or ECU.

This function is known as Electronic Spark Advance (ESA) and is accomplished by Toyota's programming of the ECU. By monitoring the rpm, intake air volume, engine temperature, throttle position and other variables, the microprocessor decides the correct moment to trigger the spark for any engine operating condition from cold idle through wide open throttle. The system is simple, non-adjustable and reliable.

In addition, some early distributors have a vacuum retard mechanism which is contained in the same housing on the side of the distributor as the vacuum advance. The function of this mechanism is to retard the timing of the ignition spark under certain engine conditions. This causes more complete burning of the air/fuel mixture in the cylinder and consequently lowers exhaust emissions. Both the vacuum advance and the vacuum retard have vacuum hoses connected to them. Don't get them mixed up during removal.

Because these mechanisms change ignition timing, it is necessary to disconnect and plug the one or two vacuum lines from the distributor 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 in 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. This will cause the piston to be forced down only a portion of its travel, resulting in poor engine performance and lack of power.

INSPECTION AND ADJUSTMENT



Ignition timing adjustment is checked with a timing light. This instrument is inductively connected to the number one (No. 1) spark plug of the engine as well as to the two battery terminals. 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.

Except for the 3F-E engine, the crankshaft pulley and the front cover of the engine are marked with a timing pointer and a timing scale. On Land Cruisers with the 3F-E, the timing mark is found be removing the small rubber plug at the rear of the engine where it meets the transmission. The plug is located on the same side of the engine as the spark plugs.

When the timing pointer is aligned with the 0 mark on the timing scale, the piston in the 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.

Because your Toyota has electronic ignition, always use a timing light with an inductive pickup. This pickup simply clamps onto the No. 1 plug wire, eliminating any adapters. It is not as susceptible to crossfiring or false triggering, which may occur with a conventional light.

22-R Engine
  1. Warm-up the engine, then turn the ignition OFF . Connect a tachometer to both battery terminals and to the service connector coming from the distributor.
  2.  
  3. Clean off the timing marks. The marks are on the crankshaft pulley and timing cover. The timing notches in the crankshaft pulley are normally marked at the factory with red or white paint. You may want to retouch them if they are dark, using chalk or paint. Fluorescent (dayglow) paint is excellent for this purpose. You might have to bump the engine around with the starter (just touch the key to the START position very briefly) to find the pulley marks.
  4.  
  5. Connect a timing light according to the manufacturer's instructions.
  6.  
  7. Disconnect the vacuum line(s) from the distributor vacuum unit. Clamp or plug the line(s); golf tees are excellent for this job. Any vacuum leak will make the engine run poorly.
  8.  

On 22R engines with High Altitude Compensation (HAC) systems, there are two vacuum hoses which connect to the distributor. Both must be disconnected and plugged.

  1. Be sure that the all wires are clear of the fan and moving belts, pulleys etc. Start the engine.
  2.  


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

  1. Allow the engine to run at idle speed with the gear shift in Neutral (manual) and Park (P) with automatic transmission. Use the tachometer to check idle speed and adjust the idle if necessary.
  2.  


CAUTION
Be sure that the parking brake is set and that the front wheels are blocked to prevent the vehicle from rolling.

  1. Point the timing light at the marks indicated in the chart and illustrations. With the engine at idle, timing should be at the specification given on the "Tune-Up Specifications'' chart.
  2.  
  3. If the timing is not at the specification, loosen the pinch bolt (hold-down 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, timing is correct. Tighten the hold-down bolt.
  4.  

Remember that you are using metal tools on a running engine. Watch out for moving parts and don't touch any of the spark plug wires with the wrench.

  1. Recheck the timing. Stop the engine; disconnect the tachometer and timing light. Except for engines equipped with HAC, connect the vacuum line(s) to the distributor vacuum unit.
  2.  
  3. On engines with HAC (identified in the NOTE earlier), after setting the initial timing, reconnect the vacuum hose at the distributor. Recheck the timing. It should now be about 13° BTDC.
  4.  
  5. If the advance is still about 8°, pinch the hose between the HAC valve and the three way connector. It should now be about 13°. If not, the HAC valve should be checked for proper operation.
  6.  

22R-E, 3VZ-E and 3F-E Engines

See Figures 1, 2, 3 and 4

  1. Warm up the engine, then turn it OFF . Connect a timing light to the engine following the manufacturer"s instructions.
  2.  
  3. Connect a tachometer to both battery terminals. Connect the tachometer probe to the IG-terminal in the check connector box. The check connector box is located next to the underhood fuse and relay box on trucks and 4Runner's; for Land Cruisers, the check connector box is on the firewall. Use the correct adapter to insure a tight fit on the terminal. Not all tachometers, particularly older ones are electrically compatible with this system. Read instructions for your unit before using.
  4.  



Click image to see an enlarged view

Fig. Fig. 1: Attach the tachometer as shown

  1. Start the engine and run it at idle. Check the idle speed on the tachometer; adjust it to specification if necessary.
  2.  
  3. At the check connector, use a small jumper wire to short the connector at terminal T or TE1 and terminal E1, of the DLC1 as shown. Special service tool (SST) 09843-18020 or its equivalent can be used for this also.
  4.  



Click image to see an enlarged view

Fig. Fig. 2: Connect the SST or jumper wire to the TE1 and E1 terminals of the DLC1

This jumper will be used repeatedly during diagnostics in later sections. Take the time to make a proper jumper with correct terminals or probes. It's a valuable special tool for very low cost.

  1. Check the idle speed, then check the ignition timing. The 22R-E should read 5° BTDC, 3VZ-FE should read 10° BTDC and the 3F-E should read 7° BTDC. All of these readings are at idle.
  2.  



Click image to see an enlarged view

Fig. Fig. 3: On 3-FE engines, remove the rubber plug at the rear of the engine to view the timing mark



Click image to see an enlarged view

Fig. Fig. 4: On other engines, the timing mark is visible on the crankshaft pulley

  1. Loosen the distributor pinch bolt just enough that the distributor can be turned. Aim the timing light at the marks on the crankshaft pulley (or the drive plate on 3F-E) and slowly turn the distributor until the correct timing mark aligns with the pointer. Tighten the distributor pinch bolt.
  2.  
  3. Remove the jumper wire or special service tool (SST) from the DLC1.
  4.  
  5. Check that the ignition timing advances. At idle the 22R-E should read 10°-14° BTDC, 3VZ-FE should read 8° BTDC, and the 3F-E should read 12° BTDC.
  6.  
  7. Shut the engine OFF and remove the timing light and tachometer leads.
  8.  

1FZ-FE Engine

See Figures 5, 6 and 7

Toyota's hand-held tester or an equivalent OBD-II scan tool must be used for this procedure.

  1. Warm the engine to normal operating temperature.
  2.  
  3. Connect an OBD-II compliant scan tool to the DLC3 located under the dash on the driver's side. Refer to Driveability & Emission Controls for more information.
  4.  



Click image to see an enlarged view

Fig. Fig. 5: An OBD-II compliant scan tool must be connected to DLC3

  1. Connect the timing light to the engine.
  2.  
  3. Race the engine to 2500 rpm for approximately 90 seconds. Check the idle speed. It should read 600-700 rpm.
  4.  
  5. Using SST 09843-18020 or its equivalent jumper wire, connect terminals TE1 and E1 of the DLC1 under the hood.
  6.  



Click image to see an enlarged view

Fig. Fig. 6: SST 09843-18020 or a jumper wire may be used to connect terminals TE1 and E1 of the DLC1

  1. With the transmission in neutral and the A/C off, check the timing. It should read 3° BTDC at idle.
  2.  



Click image to see an enlarged view

Fig. Fig. 7: The timing should be 3° BTDC at idle

  1. Loosen the hold-down bolt, and adjust it by turning the distributor. Tighten the hold-down bolt to 13 ft. lbs. (18 Nm), then recheck the ignition timing again.
  2.  
  3. Remove the jumper wire from the DLC1.
  4.  
  5. Check the timing, the reading should be 2°-13° BTDC at idle. The timing mark will move in this range.
  6.  
  7. Disconnect the timing light from the engine.
  8.  
  9. Disconnect the scan tool.
  10.  

2RZ-FE and 3RZ-FE Engines

See Figures 5, 8 and 9

Toyota's hand-held tester or an equivalent OBD-II scan tool must be used for this procedure.

  1. Warm the engine to normal operating temperature.
  2.  
  3. Connect an OBD-II compliant scan tool to the DLC3 located under the dash on the driver's side. Refer to Driveability & Emission Controls for more information.
  4.  
  5. Connect the timing light to the engine.
  6.  
  7. Using SST 09843-18020 or its equivalent jumper wire, connect terminals TE1 and E1 of the DLC1 under the hood.
  8.  



Click image to see an enlarged view

Fig. Fig. 8: Using the SST 09843-18020 or a jumper wire, connect terminals TE1 and E1 of the DLC1

  1. After the engine speed is kept at about 1000 rpm for 5 seconds, check that it returns to idle speed.
  2.  
  3. Check the ignition timing, the reading should be 3°-7° BTDC at idle.
  4.  



Click image to see an enlarged view

Fig. Fig. 9: The timing should be between 3° and 7° BTDC at idle

  1. Remove the jumper wire from the DLC1.
  2.  
  3. Recheck the timing, the mark ranges from 7°-18° BTDC at idle.
  4.  
  5. Disconnect the scan tool.
  6.  
  7. Disconnect the timing light.
  8.  

 
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