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Cost: $20
Difficulty:
Time: 30min
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A spark plug is an important part of the ignition system
as it produces the spark that ignites the petrol/air mixture
in the engine's cylinder. The spark plug can have a dramatic
effect on the performance of the engine, it must therefore
be checked on a regular basis to maintain the performance
of the engine. Below are some hints on the correct replacement
procedure for spark plugs.
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| Procedure |
- Spark plug socket or spark plug tool
- Rachet, extensions and u-joints if needed
- New spark plugs
1- Identify which spark plug lead fits which cylinder. A
suggestion is to attach numbered tags to the respective leads
if no other identification is available.
2- Pull the connectors off the plugs. Do not pull on the cable.
3- Ensure that the spark plug tool is securely fitted before
trying to remove the plug.
4- Check the gap on the new plugs, see
below.
5- Fit the new plugs with a little piece of plastic tube and
tighten to finger tight.
6- Using a spark plug tool, tighten the plugs between ½ and
¾ of a turn from finger tight. Refer to the owner's manual
for torque specifications.
7- Fit the plug connectors in the correct firing sequence
and ensure they are securely attached to the plugs.
8- Start the engine. If it does not run smoothly, repeat step
1 to 7 and check that the plugs have not been damaged during
tightening. Check ignition leads and replace if necessary,
also check for cracked insulators, air gap etc.
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| Spark plugs appearance |
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Check this website that explains eveything about how to read spark plugs with pictures.
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| Bosch platinum +4 |
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Can you install Bosh platinum +4 in your car?
Hummmm, I don't know, basically everyone has a different opinion
if this is good or bad for the engine, and if this gives more
power or a smoother idle...
If you feel like wasting some money (these are not cheap),
you can try them... and send me an e-mail if it is working.
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| Part numbers |
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525i (89-90) M20 - 535i
Regular Bosch W8LCR Gap: 0.7-0.8 mm (0.028-0.032 in)
(On the 535i, set them slightly larger to 0.86-0.91mm (0.034-0.036in
to help improve the idle.)
Platinum Bosh W8LPR (alternate choice)
525i (91 on) M50 - 530i - 540i
Bosch F7 LDCR Non adjustable
Thanks to Joseph Phan 
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