HOW TO - General Maintenance for First Timers - Changing Spark Plugs, How to Change Spark Plugs Options

[Nial]

Changing Spark Plugs…it’s a little more scientific than most people think……………………..

Initial thoughts on this might make you think this is an easy task…it depends greatly on your cars set up, those with a FMIC or a Non turbo Celica will find this a lot easier than those with a charge cooler, I will write this as if you do still have the charge cooler/top mount inter cooler in place, if you don’t have one in the way, then simply miss those steps out

Unless your engine is fitted upside down then you do not need to jack the car up for this task.

Parts Needed

Spark Plugs

For a basic spark plug change then that is all you will need, I will go through some checks that you should perform which might require the purchase of some other parts. But will get to that later.

There are a million and one spark plugs to choose from, copper core, Platinum, iridium and silver, multi electrode, splitfire, then theres the heat ranges… blah blah blah…the list is endless. Iridium spark plugs have a bit of a hit and miss result in a GT4 and IMO are over priced & well avoided, some will say…”Well I have had them for years and they have always been fine in my car…for everyone that does that could find a person that hasn’t got on well with them, I’d say your chances are 60/40 in favour of them working OK. Platinum spark plugs are slightly more expensive but so far have a 100% success rate in a GT4…silver plugs have only been tried by a few…I have had them, but for the money…forget it.
Despite popular belief and what nearly every car shop will tell you, Platinum & Iridium spark plugs are NOT performance spark plugs, they are now marketed as such but they were originally designed as long life plugs for modern engines that have long service intervals and only the very tips are made of these fancy metals which are less conductive than copper….if you want to fit some and not have to change the plugs again for 50,000 miles then go ahead and buy some…if you are like me and change them maybe once a year then normal copper core plugs are spot on….they are a fraction of the cost and perform just as well as, or even better than iridium or platinum plugs…don’t be fooled into spending £50 on a set of plugs when £10 is all you need to spend (you can see why they do it now eh!)

Heat Ranges…many of you have heard about spark plug heat ranges but possibly have no idea what the difference is - The major structural difference affecting the heat rating is the length of the insulator nose. A hot type spark plug has a longer insulator nose than a cold type spark plug The insulator nose of a hotter spark plug has a longer distance between the firing tip of the insulator, and the point where insulator meets the metal shell. Therefore, the path for the dissipation of heat from the insulator nose to the cylinder head is longer and the firing end stays hotter. The insulator nose of a hotter spark plug also has a greater surface area that is exposed to more of the ignited gases and is easily heated to its optimal operating temp, but can overheat in high boost engines as it has less protection. A colder spark plug functions in an opposite manner, it takes longer to reach its optimal working temperature, but is protected more from the higher heat generated by higher boost so is less likely to over heat.

Gapping a spark plug. All spark plugs come pre gapped and don’t need changing for a more or less standard car…even some degree of modification will still not require the plugs to be re-gapped. 0.9 mm is the usual spark plug gap and is fine up to 1.3 bar and even higher…you may want to reduce this to 0.8mm or even 0.7mm if you are running even higher levels of boost.

Tools needed


10mm – 12mm – 14mm spanners and/or sockets with ratchet
Pliers
Spark plug socket or removal tool
Extension bar

This job is best done when the engine is cold, you don’t want to be burning yourself on a hot engine.

You will have to start by removing the charge cooler. There is a bit of a knack to this, it gets easier with experience, but for the first timer it can be a challenge at best….The charge cooler is secured to the engine by 3x 12mm bolts, two on the passenger side, one on the drivers side. You need to fully remove all three and store somewhere safe

You then need to undo three jubilee clips….one at the back of the charge cooler that secures the throttle body rubber to the charge cooler, and two at the front of the charge cooler, one that secures the turbo to charge cooler pipe in place, and the other which holds the dump valve pipe in place (this is likely to be the squeeze type which you will need the pliers for, squeeze the two tangs together and move the clamp to the centre of the pipe) Then remove the throttle cable from the front most jubilee clip which holds the turbo to charge cooler pipe to the turbo….then undo this jubilee clip.
The charge cooler has two water pipes on its passenger side, you do not need to undo or remove these, they can simply be moved out the way.

Undo the charge cooler overflow pipe which goes to the white expansion tank attached to the suspension tower brace., undo the electronic connection to the charge cooler level sensor so the wires are not put under any stress. Also undo the vacuum pipe on the back of the charge cooler that goes to the air con idle up valve.

Now slide the turbo to charge cooler pipe as far ON to the turbo as you can or remove it completely if you can manage this. The final task needed before the charge cooler can be moved out of the way, is to disconnect the throttle cable from its retainer, this is near the front drivers side of the charge cooler which just holds the cable steady, pull it out of the retainer…you might need a small screwdriver to lever it out as it can be quite hard to move.

Now lifting the charge cooler up slightly, twist it anti clockwise at the same time as pulling the front up this should release it from the pipe work…but be careful not to do it too much as to break the still attached water pipes

When the charge cooler is clear, flop it over to the passenger side (left side of the car for those who drive on the wrong side ) and rest it upside down on top of the standard airbox/suspension tower. (this negates the need to drain the charge cooler system.)

Now the charge cooler is out of the way you should have free and unfettered access to the spark plug wires, and ultimately the spark plugs.

The Spark plug wires are secured in place by a long plastic box, chances are that this has become brittle with age and heat from the engine….care should be taken when removing this from the car. New ones can not be purchased on their own. This plastic tray is held in place by some 10mm bolts Six if I remember rightly but it could be just 5……undo these with a spanner or a small ratchet and store somewhere safe….

(a good tool for this is a magnetic tray, these can be purchased from machine mart for about a tenner or from car boot sales for a fiver)

Once all the bolts are removed the plastic tray is free to move, Do not pull at it or try to move it as there is no need and you will only increase the chances of breaking it, just make sure that it is free to move. Start by removing the left most spark plug wire (cylinder #1 cam belt end) pull upward sharply with a tug…you should hear a slight click as the wire releases from the spark plug followed by a pop as the rubber protection cover releases from the rocker cover, repeat this for all 4 spark plugs working your way from left to right as you look at the engine (Cylinders #1, #2, #3 and finally #4) Flop the assembly over the distributor cap out of the way.

Now seems a silly bit, but if you can, vacuum the top of the engine, this stops foreign bodies form dropping down the spark plug hole and into the engine…DO NOT be tempted to wipe across the top of the rocker cover with a normal cloth as more than likely, any debris on the top of the engine will end up down the spark plug hole…if you must use a tack cloth which is slightly sticky and will cling on to any debris on the top of the engine.

Next a quick inspection, with a handy torch, take a look down each of the spark plug recesses, your looking for dirt and oil, if you spot dirt, remove it all before removing the spark plug or it can drop into your engine, oil isn’t so much of an issue unless there is lots of it, a bit of oil is OK, a lot may cause hydraulicing of the engine, so again remove it all with a suitable cloth before removing the spark plug.

If there is oil in either of the outer spark plug recesses, then you need to replace the outer rocker cover gasket (Part # 11213-88480) if either of the inner spark plug recesses are full of oil then you need to replace the inner rocker cover gasket (Part # 11214-88480) part numbers are for the 3sgte.

Once you are sure that no oil or dirt can fall into the engine then you are ready to remove the plugs

The GT4 requires an XXmm (can't remember, will need to check) sized spark plug socket or removal tool, If you are using a socket, then you will need a 10” extension bar too as they are quite far down….a spark plug removal tool should be long enough as it is.

Start by adding a bit of oil to the rubber inside the spark plug socket/removal tool, they can grip the plug quite tight and can be a a pain to separate once they are out of the engine. Start with Plug #1 at the cam wheel end of the engine…it dosnt matter which sequence you do them in, just makes sence to start with number one! Undo the plug anticlockwise, be careful to keep the socket/removal tool in line with the plug as any deviation could shear the top off the spark plug, not the end of the world but it will likely introduce contamination into the engine which you don’t want….be careful.

Once one plug is out, replace it immediately with the new plug…keep the time that the engine is open to a minimum. Torque down the plug to the required torque which off the top of my head is about 18nm, but I just tighten them to what I think is right, to the point where they start to bite, plus quarter of a turn.

When all the plugs are in place, push the spark plug wires back onto them, they will click when fitted correctly.

Redo the 10mm retaining bolts that hold the plastic wire casing in place….dont do them up very tight at all or you will crack the plastic, finger tight plus a nip up is fine…be careful

Before refitting the charge cooler use this time to inspect inside to see if its all clean with no excess oil anywhere…this will reduce its cooling ability, also check the throttle plate…make sure that no debris has managed to fall inside. Also take a look into the turbo outlet, check for oil..a little is fine but a lot of black oil should be investigated…it might be just old age, but its worth checking either way.

Now you are ready to replace the charge cooler, if you have removed the turbo to charge cooler pipe, fit this back on first to the turbo and push it on as far as it will go.

Next up, refit the charge cooler, flop it back off the airbox/suspension tower and locate it roughly in place, then lift the front of the charge cooler up and push the charge cooler on to the charge cooler to throttle body pipe pushing it on as far as it will go. Then bring down the front of the charge cooler and locate the charge cooler to turbo pipe correctly, then push the charge cooler home. (A small squirt of WD40 on the inside of the pipes helps to let them slide easily onto the charge cooler.)

Then finally line up the charge cooler to turbo pipe.

Next refit the three 12mm charge cooler retaining bolts, one on the drivers side, two on the passenger side that secure the charge cooler to the engine

Re locate the jubilee clips into the right position and do them up…remember the jubilee clip that has the throttle cable locator on it goes onto the turbo….dont forget the jubilee clip on the throttle body rubber. Do not over tighten them…if they slip the threads they will not be able to grip as tightly as they should.

Reconnect the vacuum pipe at the back of the charge cooler.

Re locate the throttle cable to the holder on the drivers side of the charge cooler

Reconnect the charge cooler level sensor

Reconnect the charge cooler overflow pipe to the expansion tank (it goes onto the lower of the two connection points.

Double check you have done everything up. You should also use this time to check the level of the fluid in the charge cooler, it should be full to the brim.

Jobs a good un. Start up the car and check for misfires…if you are happy take the car for a test run, it should be smooth and not jerky. Enjoy many happy miles of motoring ahead at least until the next plug change.

This post has been edited by Nial: Dec 23, 2013 - 1:37 AM

[blockustomz]

Nice post!

[Smaay]

where is all the pics like your last post

[Nial]

Thanks

where is all the pics like your last post

I will add some when I have edited the photos, I tend to write first, then take photos to suit.

[ILoveMySilly97]

Nial you should've added the spark plug wires along with this too. Unless you going to add that into a dizzy tune up?

[Nial]

Nial you should've added the spark plug wires along with this too. Unless you going to add that into a dizzy tune up?

I thought I would do a dizzy cap, rotor arm replacement guide separately.

[blockustomz]

Nial you should've added the spark plug wires along with this too. Unless you going to add that into a dizzy tune up?

I thought I would do a dizzy cap, rotor arm replacement guide separately.

I'd vote to put them together.. Really should do those as well.. Cheap parts