Acura Coupes and Sedans 1994-2000 Repair Information

Ignition Timing

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GENERAL INFORMATION



In timing is the measurement, in degrees of crankshaft rotation, of the point at which the spark plugs fire in each of the cylinders. It is measured in degrees before or after Top Dead Center (TDC) of the compression stroke. Ignition timing is controlled by turning the distributor in the engine.

Ideally, the air/fuel mixture in the cylinder will be ignited by the spark plug just as the piston passes TDC of the compression stroke. If this happens, this piston will be beginning the power stroke just as the compressed and ignited air/fuel mixture starts to expand. The expansion of the air/fuel mixture then forces the piston down on the power stroke and turns the crankshaft.

Because it takes a fraction of a second for the spark plug to ignite the gases in the cylinder, the spark plug must fire a little before the piston reaches TDC. Otherwise, the mixture will not be completely ignited as the piston passes TDC and the full benefit of the explosion will not be used by the engine. The timing measurement is given in degrees of crankshaft rotation before the piston reaches TDC (BTDC). If the setting for the ignition timing is 5 degrees BTDC, the spark plug must fire 5 degrees before that piston reaches TDC. This only holds true, however, when the engine is at idle speed.

As the engine speed increases, the pistons go faster. The spark plugs have to ignite the fuel even sooner if it is to be completely ignited when the piston reaches TDC. To do this, the distributor has a means to advance the timing of the spark as the engine speed increases.

If the ignition is set too far advanced (BTDC), the ignition and expansion of the fuel in the cylinder will occur too soon and tend to force the piston down while it is still traveling up. This causes engine ping. If the engine is too far retarded after TDC (ATDC), the piston will have already passed TDC and started on its way down when the fuel is ignited. This will cause the piston to be forced down for only a portion of its travel. This will result in poor engine performance and lack of power.

Timing should be checked at each tune-up. It isn't likely to change much. The timing marks consist of a notch on the rim of the crankshaft pulley or vibration damper and a graduated scale attached to the engine front (timing) cover.

There are three basic types of timing lights available. The first is a simple neon bulb with two wire connections. One wire connects to the spark plug terminal and the other plugs into the end of the spark plug wire for the No. 1 cylinder, thus connecting the light in series with the spark plug. This type of light is pretty dim and must be held very closely to the timing marks to be seen. Sometimes a dark corner has to be sought out to see the flash at all. This type of light is very inexpensive. The second type operates from the vehicle battery-two alligator clips connect to the battery terminals, while an adapter enables a third clip to be connected between No. 1 spark plug and wire. This type is a bit more expensive, but it provides a nice bright flash that you can see even in bright sunlight. It is the type most often seen in professional shops. The third type replaces the battery power source with 115 volt current.

Some timing lights have other features built into them, such as dwell meters, or tachometers. These are convenient, in that they reduce the tangle of wires under the hood when you're working, but may duplicate the functions of tools you already have. One worthwhile feature, which is becoming more of a necessity with higher voltage ignition systems, is an inductive pickup. The inductive pickup clamps around the No. 1 spark plug wire, sensing the surges of high voltage electricity as they are sent to the plug. The advantage is that no mechanical connection is inserted between the wire and the plug, which eliminates false signals to the timing light. A timing light with an inductive pickup should be used on Acura systems.

ADJUSTMENT 1.8L, 2.2L, and 2.3L Engines



  1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
  2.  
  3. If equipped with an automatic transaxle, place the shifter in Park. If equipped with a manual transaxle place the shifter in Neutral. Set the parking brake and block the drive wheels.
  4.  
  5. Start the engine and hold the engine speed at 3000 rpm, until the radiator fan comes on. The engine should be at idle speed and at normal operating temperature. Be sure all electrical accessories (radio, air conditioning, lights, etc.,) are turned OFF.
  6.  
  7. Locate the Service Check (SCS) connector:

    1.8L engines: behind the right kick panel
     
    2.2L and 2.3L engines: centrally located under the dash
     

  8.  
  9. Connect the SCS service connector part number 07PAZ-0010100 or equivalent.
  10.  
  11. Connect a timing light to the No. 1 ignition wire and point the light toward the pointer on the timing belt cover.
  12.  
  13. Check the idle speed and adjust if necessary.
  14.  
  15. The red mark on the crankshaft pulley should be aligned with the pointer on the timing belt cover.
  16.  

The white mark on the crank pulley is Top Dead Center (TDC).

  1. Adjust the ignition timing by loosening the distributor mounting bolts and rotating the distributor housing to adjust the timing. Set as follows:

    1.8L engines (Except Type R): 16 degrees Before Top Dead (BTDC) Center at 700-800 rpm
     
    1.8L engines (Type R): 16 degrees BTDC at 750-850 rpm
     
    2.2L engines: 15 degrees BTDC Center at 650-750 rpm
     
    2.2L engines: 12 degrees BTDC Center at 650-750 rpm
     

  2.  
  3. Tighten the distributor bolts to 17 ft. lbs. (24 Nm) and recheck the timing.
  4.  
  5. Remove the SCS service connector part number 07PAZ-0010100 or equivalent.
  6.  

2.5L and 3.0L Engines

These vehicles have distributors, however the ignition timing is not adjustable. The ignition timing is controlled by the Powertrain Control (PCM) Module and can be checked for diagnostic purposes. If the timing is out of specification, all mechanical and electrical systems should checked for proper operation before replacing the PCM.

  1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
  2.  
  3. To check the ignition timing, start the engine and allow it to fast idle at 3000 rpm with all electrical accessories off and the transmission in N or P . Allow the engine to warm up and reach normal operating temperature. The engine cooling fan should cycle at least one time.
  4.  
  5. Locate the Service Check (SCS) connector out from under the glove box. Connect the service connector tool part number 07PAZ-0010100 or equivalent to the SCS terminals.
  6.  
  7. Check the idle speed and adjust if necessary.
  8.  
  9. Connect a timing light to the No. 1 plug wire. While engine idles, point the light toward the pointer on the timing belt cover.
  10.  
  11. Inspect the ignition timing at idle. The specifications are as follows:

    2.5L Engine: 13-17 degrees Before Top Dead (BTDC) Center at 650-750 rpm
     
    3.0L Engine: 8-12 degrees BTDC at 700-800
     

  12.  

All mechanical and electrical systems should checked for proper operation before replacing the PCM.

  1. If the ignition timing is incorrect, replace the PCM.
  2.  
  3. Remove the service connector.
  4.  

3.2L and 3.5L Engines

These vehicles have individual ignition coils and the ignition timing is not adjustable. The ignition timing is controlled by the Powertrain Control (PCM) Module and can be checked for diagnostic purposes. If the timing is out of specification, all mechanical and electrical systems should checked for proper operation before replacing the PCM.

  1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
  2.  
  3. To check the ignition timing, start the engine and allow it to fast idle at 3000 rpm with all electrical accessories off and the transmission in N or P . Allow the engine to warm up and reach normal operating temperature. The engine cooling fan should cycle at least one time.
  4.  
  5. Locate the Service Check (SCS) connector under the glove box and connect the service connector tool part number 07PAZ-0010100 or equivalent to the SCS terminals.
  6.  
  7. Check the idle speed and adjust if necessary.
  8.  
  9. Connect a timing light to the No. 1 plug wire. With the engine idling at normal operating temperature point the timing light toward the pointer on the timing belt cover.
  10.  
  11. Inspect the ignition timing. The specifications are as follows:

    3.2L Engine: 13-17 degrees Before Top Dead (BTDC) Center at 590-690 rpm
     
    3.5L Engine: 13-17 degrees BTDC at 700-800 rpm
     

  12.  

See Figures 1 and 2

Click image to see an enlarged view

Fig. Fig. 1: Service check connector-3.2TL and 3.5RL



Click image to see an enlarged view

Fig. Fig. 2: Timing light attachment-3.2TL

All mechanical and electrical systems should checked for proper operation before replacing the PCM.

  1. If the ignition timing is incorrect, replace the PCM. Only replace the PCM as a last resort.
  2.  
  3. Remove the timing light.
  4.  
  5. Disconnect the special tool (SCS service connector) from the service check connector.
  6.  

 
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