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Spark Plugs and Wires
 
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Pelican Technical Article:

Spark Plugs and Wires

Steve Vernon

Time:

2 hours2 hrs

Tab:

$12 to $200

Talent:

**

Tools:

13/16th spark plug socket, extension, 10mm wrench if you are replacing the wires

Applicable Models:

BMW E10 2002 Coupe/Conv (1967-76)
BMW E21 320i Coupe (1977-83)

Parts Required:

Spark plugs, wires if needed

Hot Tip:

Work on a cold engine

Performance Gain:

Better mileage

Complementary Modification:

New air filters

One basic tune-up procedure for just about any car on the road is the replacement of your spark plugs and spark plug wires (where applicable). I recommend replacing your spark plugs every 10,000 miles, or about once a year. However, if your car is not a daily driver and only gets taken out on nice weekends you can go longer. Just make sure you pull them and check them once a year.

Begin by prepping the car. The only thing that you really need to do is to make sure that the car is cold. If you try to remove or install spark plugs in a hot car, you may encounter problems with the spark plugs gumming up or damaging the relatively delicate threads in the aluminum cylinder head. Always hand thread the new plugs in until you are sure they are properly threading.

Since the M10 engine in the 2002 is a straight four all four spark plugs (red arrows) are located on the right side of the motor and can easily be replaced without removing anything else from the engine bay.
Figure 1

Since the M10 engine in the 2002 is a straight four all four spark plugs (red arrows) are located on the right side of the motor and can easily be replaced without removing anything else from the engine bay.

The car we have the pleasure of working on is the Clarion Build's BMW 2002 with a fully restored and complete motor.
Figure 2

The car we have the pleasure of working on is the Clarion Build's BMW 2002 with a fully restored and complete motor. Your engine may be missing some small part from use over the years. There should be a spark plug wire holder attached to the valve cover between the number 2 and 3 cylinders; if you are just changing plugs you do not need to move this, as you can access them with the bracket in place (red arrow).

Begin by removing the spark plug wires from the plugs.
Figure 3

Begin by removing the spark plug wires from the plugs. Pull and gently wiggle the connectors off the plug by using the plastic part of the housing on the connectors; never pull the connector off using the wire only, as you may damage the connector (red arrow).

The spark plug wires on the 2002's are old technology.
Figure 4

The spark plug wires on the 2002's are old technology. The connection consists of the lead and a small wire to hold it on the end of the plug. This is what it should look like when you look at the connection end. If your plug wires are not staying on the end of the plugs there is a good chance the small clip wire (red arrow) that holds it in place is damaged or missing.

To remove the plugs use a 13/16 spark plug socket (it does not need to be thin walled) along with an extension.
Figure 5

To remove the plugs use a 13/16 spark plug socket (it does not need to be thin walled) along with an extension. Place the socket over the plug and slowly rotate it until it seats over the rubber in the socket and the base of the plug (red arrow). These should not be torqued in the opening overly tight but for some reason people really like to over torque plugs. The torque value of your plugs should be on the spark plug boxes.

When changing the plugs take a moment and look at the condition of the old plugs.
Figure 6

When changing the plugs take a moment and look at the condition of the old plugs. You can learn a lot about the health of your motor by looking at them. Wet, oily or excessive carbon build up on plugs are all signs of trouble within your combustion chamber. The plug should look like the ones in the Clarion Build's car. A nice dry ashen color indicates a clean properly balanced air fuel mixture and no problems with the rings or cylinders. The problem we found on two of our plugs were that they were lose in the head and we got blow by coming out of the plug opening (red arrow). This area of the plug should be clear and clean. When installing new plugs do NOT use anti-seize. Regular maintenance should eliminate any chance of the plug seizing in the head. The threaded section of the plug actually works as the ground. Anti-seize can cause ground problems and poor performance. Installation of the plugs is the reverse of removal. Also always hand thread the new plugs in until you are sure they are properly threading.

If you are replacing the wires make sure to label the wires to the proper cylinders and replace them one at a time.
Figure 7

If you are replacing the wires make sure to label the wires to the proper cylinders and replace them one at a time. You will need to remove the retainer between the number 2 and 3 cylinders. When you reinstall the clip torque the nut down to 85 inch/lbs.

If you get them mixed up the firing order is printed on the valve cover.
Figure 8

If you get them mixed up the firing order is printed on the valve cover. The number one wire goes at 12 o'clock and the distributer rotates clockwise so the wires go on clockwise from 12 o'clock 1,3,4,2.


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Page last updated: Fri 12/9/2016 02:57:47 AM