How to Change BMW Spark Plugs
How to Change BMW Spark Plugs
Spark plugs are part of routine maintenance and depending on type of plugs used should be replaced every 60,000km – 100,000km. This BMW stutters on acceleration and has about 90,000km on odometer. Engine stutter is noticeable on low speed or idling mostly. No check engine light or other fault codes present.
Spark plugs are a maintenance item: When to Replace Spark Plugs on Your Car.
Replacing spark plugs on BMW 3 E90 series is a medium difficulty job, couple hours of work.
Tools Required: Spark plug socket (5/8), extension, ratchet, 8mm socket and screwdriver.
How to Change BMW Spark Plugs
Start by removing BMW Cabin Air Filter Housing (How to Remove BMW cabin filter housing).
There are 2 plastic covers (drivers and passenger side) which need to be removed. Each cover has a sensor on top. Clips are located on sides of the cover.
Unplug sensors (twist left sensor to remove) and move them to the side. Unclip and remove both covers, there are two 8mm bolts on both sides holding housing down, one on each side. Picture below (red circle).
How to Remove BMW Spark Plugs
Next, engine wiring harness. BMW E90 has two separate wiring harness boxes, one behind the other. Three clips each, pull on outer harness and will come right out. Inner harness, use a screwdriver to open clips, pull wiring out, just leave it hang on top of the engine. Picture below (red and blue circles).
Remove Cabin Filter housing: It might require a bit of force, it’s a used car and time will get things seized. Just pull on it.
Remove engine cover Allen key bolts and move cover aside.
BMW engine ignition coils will be visible now. Red arrows picture below.
Unplug coils connectors: To unplug a coil electrical connector, lift retaining clip up and pull connector plug out.
How to Change BMW Spark Plugs
Be careful as ignition coils are fragile (and cheaply made). If Ignition Coils are seized, twist them while pulling them out. Again, take your time and be careful as these things break easily.
Remove Spark Plugs: Use spark plug socket and extension to remove spark plugs. Number five will be a bit tricky as it has a stability bar on top of it.
Spark plug removal tool from a BMW E39 used on picture below, from times when BMW had a spark plug tool in their cars toolbox. Today they can not be bothered for a dipstick or a temperature gauge.
After removing spark plugs, inspect plug holes. If you see oil inside spark plug housing, valve cover gasket and spark plug gaskets need to be changed.
How to Install New Spark Plugs
New spark plugs should be screwed in by hand. Do not use of a ratchet or force. Use only extension and spark plug socket (Do not use a Ratchet). Put a plug on the socket and screw it in by hand. It should go in smooth and easy.
How to Change BMW Spark Plugs:
If you have difficulties to screw a spark plug by hand, do not force it in. Take it out and check whats going on. Maybe there is dirt on spark plug threads or you got a faulty new spark plug. Try another spark plug or try to thread spark plug on another spark plug hole.
Install new spark plugs by hand only initially. Do no use a ratchet or force. Insert a spark plug on spark plug socked and thread spark plug as much as you can by hand. Use ratchet only to tighten them after hand installation. Don’t over-tighten spark plugs. It take half at turn or so after hand installation to fully tighten them.
Forcing spark plugs by force is asking for big trouble. If you mess up spark plug threads on engine block, your wallet will be in line for pain.
Push coils in firmly and plug electrical connections. Put remaining back together and start engine to make sure everything works fine.
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