Replacing Spark Plugs

Replacing the spark plugs is another one of those easy-to-do routine maintenance procedures that can be done quickly with a minimum number of tools. However, as with many procedures of this type, it is still possible to inflict expensive damage to your engine if things are not done properly. If you do not feel comfortable doing it, you should probably leave it up to a mechanic or more knowledgable do-it-yourselfer.

The procedure outlined here pertains directly to the Honda B16A2 motor found in the 1999-2000 Civic SiR (in Canada) and Civic Si (in the US). Other vehicles may require different procedures to replace the spark plugs - consult a shop manual for your particular vehicle for best results.

To the right is a photo of the area we will be working in. If you are not familiar with the basics of what you see in this photo (distributor, spark plug wires, valve cover, etc.), again, you may want to leave this up to a mechanic or mechanically inclined friend.

Replacing the spark plugs should be done with the engine cold, according to the Haynes manual. Besides, the head gets really hot, even when the engine is just warmed up, so it would be pretty painful trying this with a warm engine...

To the right is a photo of the tools required for this procedure. What we have here is a spark plug socket (mine came with my socket set - make sure you have the correct size), a nice long socket extension, a spark plug gapping tool, 10mm socket, a full set of spark plugs (make sure you have the exact correct ones for your vehicle - more on this in a moment), and some anti-seize for the threads on the plugs.

Spark plugs come in a dazzling array of shapes, sizes, heat ranges, and compositions. Using the correct plug for your particular engine is very important. Not only is the spark plug a huge part of the combustion process, the plug itself protrudes into the combustion chamber, and using the incorrect plug could possibly lead to the plug coming in contact with the piston dome. Consult an owner's manual or shop manual for your particular vehicle to find out which spark plugs you should be using.

In my case, I am actually not using the spark plugs recomended by Honda. Honda recommends a platinum spark plug for the B16A2, but I prefer a copper plug due to it's lower cost and ever so slight performance advantage. Because of this, I have to replace the plugs more often, but since the copper plugs cost considerably less than the platinum plugs, I am not actually spending any more money replacing the coppers more often.

In order to make sure I am using the correct copper plug for my vehicle, I contacted NGK to find out the correct copper replacement for the platinum plugs in my vehicle.

Step one is to remove the plastic spark plug wire cover found on Honda DOHC B-series engines. This is done by removing the four 10mm nuts that hold it in place. The cover is plastic, so be carful when re-installing this piece because it is possible to overtighten and crack it.

Once the spark plug wire cover is off, take note of how the spark plug wires are arranged in their guides. On the B16A2, there are three spark plug wire guides on top of the valve cover, but only two will need to be manipulated for this procedure.

Before going any further, use some compressed air or a shop vac to remove any dirt/sand/grit/debris from this area. Although the wire cover does a fairly good job of protecting this area, sand and grit still gets in, and any debris that is left can fall into the spark plug holes and eventually into the engine - not a good thing!

Step two is to gap the new plugs. This is where the spark plug gapping tool comes in. Feeler gauges are not recommended for this procedure. Gapping tools are cheap and can be found at any automotive parts supplier - mine is from Canadian Tire.

On the gapping tool, find the correct gap recommended for your particular vehicle. This information can be found in a shop manual or from NGK. In my case, 0.050" was the recommended gap, so using the 0.050 gauge, I checked each plug before installation. As one would expect, the gap is never correct out of the box, so the correct gap will have to be set on each new plug before installation.

Using the spark plug gapping tool, carefully bend the electrode a tiny bit at a time (as shown in the photo to the left - sorry the photo is a bit messed up), until the gapping tool slides in and out between the electrode and the tip, with a bit of friction.

Step three is to remove the first spark plug wire from the cylinder furthest from the distributor (the rightmost cylinder in these photos). I prefer to do one plug at a time to ensure I know which plugs came from where and so that the correct splark plug wire goes on it's corresponding spark plug.

Remove the spark plug wire by grasping the rubber head as shown in the photos. Do not pull by the wire itself. A little bit of twisting should dislodge the spark plug wire from the spark plug, and the wire can be pulled out and away from the spark plug hole.

As you remove each respective spark plug wire, make note of which wire goes to which cylinder and how the wires are arranged in the guides. It is not necessary to unplug the wires from the distributor for this procedure, and doing so just complicates things immensely. Leave the wires attached to the distributor, and make note of how the wires are arranged, and it will be easy to replace the wires properly in the end.

The wire for this cylinder will come out only about as far as shown in the left photo. To get it out any further, you will need to remove the first guide.

The guide is removed without tools, by squeezing the plastic tab as shown at right, and pulling upwards. There is no need to unbolt the metal tab that the guide connects to. With this guide off, the first and second cylinders will be easily accessible.

At this point, before removing the old plug, I vacuumed out the spark plug hole with a shop vac, just to get any possible hint of debris out of there before exposing the internals of the engine to possible outside contamination. Remember, once the spark plug is out of its hole, the inside of the engine is fully exposed - through the spark plug hole is the combustion chamber, the top of the piston, the piston rings, and beyond that the crankshaft. Anything that gets in there can wreak havoc in a "worst case scenario".

Next, using the spark plug socket and a long extension (mine is 12 inches! You don't hear that phrase from people very often...at least truthfully), remove the first spark plug. Spark plug sockets (at least all the ones I have seen) have a rubber "gasket" in them that grabs the spark plug. Once the plug is loose, it can be lifted out of the hole using the grip of the rubber gasket. If the gasket does not take hold, try again, and make sure the plug is definitely 100% loose. One problem I had was the gasket would pop out of the socket and stay behind with the plug. If you get the technique right, this should not happen, but the first few tries it is something to watch out for.

Once the plug is free, pull it from the spark plug socket and make sure the rubber gasket does not come out with it, and make sure you put the gasket back into the socket if it does come out.

Next, put some anti-seize compound on the new, properly gapped plug. The anti-seize will ensure the plug is easy to remove the next time you replace plugs. Anti-seize is available at any auto parts store.

Once the anti-seize is applied, place the new plug in the socket, where the rubber gasket will hold it in place.

Here is the tricky part. Tricky in terms of, if you screw this up (pun intended), you are screwed (very punny). Using only the socket and extension, without a ratchet, carefully place the new plug in the hole. Make sure the plug is going in as straight as possible once it is down in the hole, and find the spark plug threads by hand. It is important that you do this step by hand, without a ratchet, because it is very easy to cross thread and strip the spark plug hole threads.

It may take a couple of tries, but the spark plug must thread in very easily. If you feel any initial resistance, back off and try again. Better safe than sorry. Again, if you cannot find the thread, make sure the plug is going in as straight as possible. It should turn quite a few rotations before you feel the resistance of the plug seating down onto it's compression washer.

Once the plug starts to seat down on it's compression washer, you can pop the ratchet on to the end of the extension and snug it down. Here is another tricky part - do not overtighten the spark plug. This is the second place where you can screw up and cost yourself a lot of headache and moo-lah. The plug just has to seat down on it's compression washer and make good contact with the head. It does not need to be superhuman-tight.

After each plug is done, go on to the next plug. Once they are all done, put the leads back on their respective plugs, making totally sure that each lead goes to the correct plug (it is somewhat obvious due to the length of each lead). The leads simply push onto each plug and seat themselves over the lip of the hole. You can feel a somewhat vague "click" as each lead seats home on the plug.

Reinstall the guides, push the wires into the guides, replace the plastic wire cover (again, do not overtighten, as it can crack), and Viola! we're done. We now have a fresh set of properly gapped plugs in place for optimum performance and efficiency.