Toyota 4Runner 2001-06

Spark Plugs

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Inspection



Check the plugs for deposits and wear. If they are not going to be replaced, clean the plugs thoroughly. Remember that any kind of deposit will decrease the efficiency of the plug. Plugs can be cleaned on a spark plug cleaning machine, which can sometimes be found in service stations, or you can do an acceptable job of cleaning with a stiff brush. If the plugs are cleaned, the electrodes must be filed flat. Use an ignition points file, not an emery board or the like, which will leave deposits. The electrodes must be filed perfectly flat with sharp edges; rounded edges reduce the spark plug voltage by as much as 50%. Check the spark plug for any thread damage and insulator damage. If any damage is detected, the spark plug must be replaced.

Check the spark plug gap before installation. The ground electrode (the L-shaped one connected to the body of the plug) must be parallel to the center electrode and the specified size wire gauge (please refer to the Tune-Up Specifications chart for details) must pass between the electrodes with a slight drag.

Always check the gap on new plugs, as they are not always set correctly at the factory. Do NOT use a flat feeler gauge when measuring the gap on a used plug, because the reading may be inaccurate. A wire-type gapping tool is the best way to check the gap. Wire gapping tools usually have a bending tool attached. Use that to adjust the side electrode until the proper distance is obtained. Absolutely NEVER attempt to bend the center electrode. Also, be careful NOT to bend the side electrode too far or too often as it may weaken and break off within the engine, requiring removal of the cylinder head to retrieve it.

Inspection & Gapping





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Fig. Checking the spark plug gap with a wire feeler gauge



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Fig. Adjusting the spark plug gap



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Fig. If the spark plug is in good condition, the electrode may be filed flat-WARNING: Do NOT file platinum plugs



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Fig. Inspect the spark plug to determine engine running conditions

Check the plugs for deposits and wear. If they are not going to be replaced, clean the plugs thoroughly. Remember that any kind of deposit will decrease the efficiency of the plug. Plugs can be cleaned on a spark plug cleaning machine, which can sometimes be found in service stations, or you can do an acceptable job of cleaning with a stiff brush. If the plugs are cleaned, the electrodes must be filed flat. Use an ignition points file, not an emery board or the like, which will leave deposits. The electrodes must be filed perfectly flat with sharp edges; rounded edges reduce the spark plug voltage by as much as 50%.

Check the spark plug gap before installation. The ground electrode (the L-shaped one connected to the body of the plug) must be parallel to the center electrode and the specified size wire gauge (please refer to the Tune-Up Specifications chart for details) must pass between the electrodes with a slight drag.

Always check the gap on new plugs, as they are not always set correctly at the factory. Do NOT use a flat feeler gauge when measuring the gap on a used plug, because the reading may be inaccurate. A wire-type gapping tool is the best way to check the gap. Wire gapping tools usually have a bending tool attached. Use that to adjust the side electrode until the proper distance is obtained. Absolutely NEVER attempt to bend the center electrode. Also, be careful NOT to bend the side electrode too far or too often as it may weaken and break off within the engine, requiring removal of the cylinder head to retrieve it.

Removal & Installation





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Fig. On the 5VZ-FE engine, you must remove the coil for access to the spark plug



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Fig. Use a 3/8 in. ratchet, a locking extension, and a spark plug socket to reach the spark plugs which are deep down in the cylinder head



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Fig. Once loosened, carefully withdraw the spark plug from the cylinder head



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Fig. View of a twin electrode plug that is found in the 5VZ-FE engine

Remove the spark plugs and wires one at a time to avoid confusion and incorrect wiring during installation.

  1. Disconnect the negative battery cable, and if the vehicle has been run recently, allow the engine to thoroughly cool.
  2.  
  3. On engines equipped with spark plugs, carefully twist the spark plug wire boot to loosen it, then pull upward and remove the boot from the plug. Be sure to pull on the boot and not on the wire, otherwise the connector located inside the boot may become separated.
  4.  
  5. On engines with coil-over-plug ignition, remove the ignition coil for access to the spark plug. For additional information, please refer to the following topic(s): Engine Electrical, Ignition Coil.
  6.  
  7. Using compressed air, blow any water or debris from the spark plug well to assure that no harmful contaminants are allowed to enter the combustion chamber when the spark plug is removed. If compressed air is not available, use a rag or a brush to clean the area.
  8.  

Remove the spark plugs when the engine is cold, if possible, to prevent damage to the threads. If removal of the plugs is difficult, apply a few drops of penetrating oil or silicone spray to the area around the base of the plug, and allow it a few minutes to work.

  1. Using a spark plug socket that is equipped with a rubber insert to properly hold the plug, turn the spark plug counterclockwise to loosen and remove the spark plug from the bore.
  2.  


WARNING
It is recommended that you NOT use a flexible extension on the socket. Use of a flexible extension may allow a shear force to be applied to the plug. A shear force could break the plug off in the cylinder head, leading to costly and frustrating repairs.

To install:

  1. Inspect the spark plug boot for tears or damage. If a damaged boot is found, the spark plug wire must be replaced.
  2.  
  3. Using a wire feeler gauge, check and adjust the spark plug gap. When using a gauge, the proper size should pass between the electrodes with a slight drag. The next larger size should not be able to pass while the next smaller size should pass freely.
  4.  
  5. Carefully thread the plug into the bore by hand. If resistance is felt before the plug is almost completely threaded, back the plug out and begin threading again. In small to reach areas, an old spark plug wire and boot or a short length of rubber hose, placed on the spark plug, could be used as a threading tool. The boot will hold the plug while you twist the end of the wire and the wire is supple enough to twist before it would allow the plug to cross-thread.
  6.  


WARNING
Do NOT use the spark plug socket to thread the plugs. Always carefully thread the plug by hand or using an old plug wire to prevent the possibility of cross-threading and damaging the cylinder head bore. Remember, your truck has aluminum cylinder heads and the spark plug threads in the head are easily damaged.

  1. Carefully tighten the spark plug. If the plug you are installing is equipped with a crush washer, seat the plug, then tighten about 1 / 4 turn to crush the washer. If you are installing a tapered seat plug, tighten the plug to 11-15 ft. lbs. (15-20 Nm).
  2.  
  3. If equipped with coil-over-plug ignition, install the ignition coil assembly(ies).
  4.  
  5. If equipped with spark plugs, apply a small amount of silicone dielectric compound to the end of the spark plug lead or inside the spark plug boot to prevent sticking, then install the boot to the spark plug and push until it clicks into place. The click may be felt or heard, then gently pull back on the boot to assure proper contact.
  6.  



Click image to see an enlarged view

Fig. You must remove the coil for access to the spark plug



Click image to see an enlarged view

Fig. Use a 3/8 in. ratchet, a locking extension, and a spark plug socket to reach the spark plugs which are deep down in the cylinder head



Click image to see an enlarged view

Fig. Once loosened, carefully withdraw the spark plug from the cylinder head



Click image to see an enlarged view

Fig. View of a twin electrode plug that is found in the 3.4L (5VZ-FE) Engine


NOTE
Remove the spark plugs and wires one at a time to avoid confusion and incorrect wiring during installation.

  1. Disconnect the negative battery cable, and if the vehicle has been run recently, allow the engine to thoroughly cool.
  2.  
  3. Remove the spark plug-s individual ignition coil for access to the spark plug. For additional information, please refer to the following topic: Engine Electrical, Ignition Coil Pack.
  4.  
  5. Using compressed air, blow any water or debris from the spark plug well to assure that no harmful contaminants are allowed to enter the combustion chamber when the spark plug is removed. If compressed air is not available, use a rag or a brush to clean the area.
    NOTE
    Remove the spark plugs when the engine is cold, if possible, to prevent damage to the threads. If removal of the plugs is difficult, apply a few drops of penetrating oil or silicone spray to the area around the base of the plug, and allow it a few minutes to work.

  6.  
  7. Using a spark plug socket that is equipped with a rubber insert to properly hold the plug, turn the spark plug counterclockwise to loosen and remove the spark plug from the bore.
    WARNING
    It is recommended that you NOT use a flexible extension on the socket. Use of a flexible extension may allow a shear force to be applied to the plug. A shear force could break the plug off in the cylinder head, leading to costly and frustrating repairs.

  8.  

To install:

  1. Inspect the spark plug boot for tears or damage. If a damaged boot is found, the spark plug wire must be replaced.
  2.  
  3. Using a wire feeler gauge, check and adjust the spark plug gap. When using a gauge, the proper size should pass between the electrodes with a slight drag. The next larger size should not be able to pass while the next smaller size should pass freely.
  4.  
  5. Carefully thread the plug into the bore by hand. If resistance is felt before the plug is almost completely threaded, back the plug out and begin threading again. In small to reach areas, an old spark plug wire and boot or a short length of rubber hose, placed on the spark plug, could be used as a threading tool. The boot will hold the plug while you twist the end of the wire and the wire is supple enough to twist before it would allow the plug to cross-thread.
    WARNING
    Do NOT use the spark plug socket to thread the plugs. Always carefully thread the plug by hand or using an old plug wire to prevent the possibility of cross-threading and damaging the cylinder head bore. Remember, your truck has aluminum cylinder heads and the spark plug threads in the head are easily damaged.

  6.  
  7. Carefully tighten the spark plug. If the plug you are installing is equipped with a crush washer, seat the plug, then tighten about 1 / 4 turn to crush the washer. If you are installing a tapered seat plug, tighten the plug to 13 ft. lbs. (18 Nm).
  8.  
  9. Apply a small amount of silicone dielectric compound to the end of the spark plug lead or inside the spark plug boot to prevent sticking, then install the boot to the spark plug and push until it clicks into place. The click may be felt or heard, then gently pull back on the boot to assure proper contact.
  10.  
  11. Install the ignition coil assemblies.
  12.  

 
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