Twinair air filter, spark plugs & coil replacement

Hello all,

I've just discovered a similar guide existing in a text only version but I thought I'd add my version with the pictures. This is a very simple job, I'm in no way mechanically minded and tend to approach everything with a ham fisted frustration that results in everything being broken and me storming off in a huff at the slightest little hiccup.

The air filter and spark plugs should be changed at every 18000 mile service but why not save yourself the labour charges and do it yourself. I would change the oil and filter at the same time but since my scale replica of the Exxon Valdez disaster in my garage last year, I refuse to touch sump plugs again. Anyways, onto the guide.

10mm socket
7mm socket
16mm spark plug socket (preferably a thin walled one as space is tight)
Extension bars for the sockets, at least 250mm for the spark plug socket and 100mm for the 10mm/7mm sockets.
Clic-R pliers or pinch pliers.
Flat bladed screwdriver
75mm jubilee clip (optional)

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[BREAK=Removing the engine cover]

Remove the three bolts with a 10mm socket. The air intake hose on the right can then be lifted out of its bracket.

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The next step is to remove the Clic-R clip on the hose at the front left of the engine cover. I borrowed the 'correct' tool from a friend (I think they're Sealey) but to be honest, they're too weak to undo the clip so I just flipped it open with a flat bladed screwdriver.

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Now you are ready to remove the engine cover. Slide it towards you, if you look down the back of it you will see the locating plug:

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Keep pulling it foward until it is free. Remove the air hose (the one with the Clic-R clip on it) and the engine cover will be free.

[BREAK=Changing the air filter]

Turn the engine cover upside down and remove the 6 bolts/screws with a 7mm socket. These won't come out completely, keep unscrewing them until they are loose and are free to move up and down.

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Lift the air filter cover out and turn it upside down. Lift out the old air filter and admire the filth - apparently mine was changed 10000 miles ago. Ohhh I love garages that play these kind of practical jokes on me.

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Brush any dust/dirt out of the filter box and pop in the new filter. Place it back on the engine cover and tighten up the 6 bolts.

[BREAK=Removing the coils]

With the engine cover off, access to the coils is easy. If you are changing the coils, remove the electrical connectors - lift the black tab, pull the yellow bit outwards and remove the connector.

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As I was only changing the plugs, I left the coils connected to the loom as having no dexterity or patience would result in one of them being broken.

Remove the bolt of top of each coil with a 10mm socket.

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Pull out the coils, they're just rubber gripping onto the spark plugs so a good tug will free them up.

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[BREAK=Removing the spark plugs]

With the coils removed, you'll have access to the plugs. You'll need the 16mm spark plug socket and a long extension bar. Being an unorganised idiot, I couldn't find my 1/2 inch to 3/8 adaptor so couldn't use any of my lovely new 1/2 inch extensions or ratchets. I bodged a long extension from two shorter 3/8 ones I found lying around which seemed to work.

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The plugs shouldn't be too tight, undo them and lift them out. If you've used an actual spark plug socket the plug should 'stick' inside it because they've got a rubber ring which grips onto the plug unlike a standard socket.

My plugs were apparently 10000 miles old, I have no idea if they are or not but I don't think these would last until 18000 miles.

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To put the new plugs in, remove the ratchet handle, put the plug into the socket and screw it in by hand with just the extension bar. This helps you to get more feel to avoid cross threading it. Pop the ratchet handle back on to tighten them up.


Put the coils back onto the spark plugs - push them down and tighten up the bolt with the 10mm socket.

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If you removed the coils, replace the electrical connector ensuring you push the yellow clip back in.

Put the engine cover back on:
I find it easier to push the air hose back on first before locating it in the 'lug' at the back of the engine. Put the 3 x 10mm bolts back in to secure the engine cover then make sure to push the air intake pipe on fully. You should feel it 'bump' over the ridges on the engine cover, when it's fully seated there should be barely enough space to get the pliers wide enough to tighten the clip. If you don't push the air hose on fully it could pop off under full load/acceleration resulting in a pant-wetting bang (go on, ask me how I know...).

Either fasten up the Clic-R clip or replace with a 75mm jubilee clip.

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Job jobbed.


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New member
Oct 7, 2015
I now realise why I couldn't get the electrical connectors off of the coils - it's pull out the yellow tab then push down the black bit on top.
Apr 27, 2011
Near the M4
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