Home: Mustang Tech: Maintenance and Tune Up: 99+ Sparkplug installation
99+ Sparkplug installation
by Kevin Kunz

I picked a subject for the tech contest that most veteran Stangbangers would think was a bit amateur, but I felt that it would be helpful for the newbie wanting to upgrade or just change his or hers spark plugs on their 99+ Stang.

Bolts Torque
Throttle Body 89 in/lbs
Fuel Rail retaining bolts 89 in/lbs
Ignition Coil pack retaining bolt 89 in/lbs
Spark Plugs 11 ft/lbs

To change the spark plugs in most of the newer mustangs you have to remove the fuel rail which is the reason I am going to start out with instructions detailing the fuel system. Considering that you are working on the fuel system I would assume that most of you would know that it would be a grave mistake to smoke while you did this job or had any open flame around.

Step 1: The Mustang's fuel system is a pressurized system and before you do any work on the fuel system you have to release the pressure on the system. The way this is done is in the trunk there is a switch called an inertia switch. A wire needs to be unplugged from the bottom of the inertia switch. This will shut off the fuel pump. Please refer to picture 1.

Step 2: Start up you Mustang and let it run until it stalls, this should take a few minutes. Once the car stall it means that the pressure has been relieved in the system.

Step 3: Remove the negative terminal on your battery with a 5/16" wrench or socket. Refer to picture 2

Step 4: At this point you are going to need to remove your air cleaner outlet tubes from the throttle body. In my case I have to remove my induction tubes from my Paxton Supercharger. Refer to picture 3.

Step 5: Now you will need to remove your throttle body. This is held on by four bolts, one in each corner. Remove these four bolts. On the left side of the throttle body you will need to disconnect your throttle cable, throttle return spring and (cruise control if equipped) One the right side off the throttle body you will need to unplug the throttle position sensor. Please refer to picture 4.

Step 6: Disconnect hose from the PCV and lay it somewhere out of the way. Refer to picture 5.

Step 7: Remove the fuel line safety clip from the fuel line. I found the easiest way to remove it was to flip it upside down and give it a good firm push downward. Refer to picture 6.

Step 8: This would be a good time to put some rags underneath the fuel line near the coupling. When fuel line is disconnected a residual amount of fuel will spill out.

Step 9: Now you will need to disconnect your fuel line. You will need a special tool to do this (fuel line coupling release), most parts stores have them in stock. The one I use is a Blue point #9056-2 and it works great. You need to wrap the tool's jaws around fuel line below the quick coupling and close the jaws around the line and then pull the tool up into the bottom of the coupler and push at the same time on the fuel line and you will feel them release from each other. Move the fuel line out of your way. Refer to picture 7 and 8.

Step 10: You will now need to remove the two bolts holding the fuel rail on. Refer to picture 9.

Step 11: This is another one of those times when you will wants some rags, this time try and stuff them under the fuel rail. Rock the fuel rail back and forth and pull up at the same time. The fuel rail should pop right off and some more fuel will spill out. Don't get nervous if an injector comes out with the rail, this sometimes happens. If it does just remove the injector from the rail and push it back in the hole. Refer to picture 10.

Step 12: Now push the fuel rail out of the way so you can get to ignition coils. Refer to picture 11.

Step 13: Now you are ready to start changing plugs. Beside each fuel injector is a little black round device called a ignition coil pack and underneath it is the home of each of your plugs. I highly suggest changing one plug at a time. Tool, screws and other debris can get bumped around and one of the worst things that can happen is to drop a screw down a plug hole.

Step 14: To remove the plugs you will need to remove the ignition coil pack. To do this just remove the one bolt holding each one down with a 7mm socket or wrench and give a slight tug on it and in will pop off the plug. If the pack separates from the rubber boot and the boot won't come out of the hole, just take a pair of needle nose pliers and pull the boot out of the hole. Then push the two pieces back together. Refer to picture 12 and 13.

Step 15: Now you will need a 5/8 spark plug socket and a long extension. I really suggest you use a spark plug socket for this part because the plugs are way down in there and they will be difficult to get out without the plug socket.

Step 16: Before I actually took the plugs out, I took a really narrow attachment on my shop vac and vacuumed out the hole because there is sometimes some crap that falls down in the hole after you pull the boot off. This is just optional but I like things being clean.

Step 17: After you get the old plugs out, when you go to put the others back in, you want to just use your extension, plug socket and your fingers. You do not want to get these plugs cross threaded and it is very easy. Just ease them in there and when they get tight then put your torque ratchet on it and snug it up to 11 ft/lb. Refer to picture 14.

Step 18: Replace the ignition coil pack and boot and tighten the bolt back down (7mm socket) to 89 in/lbs. Refer to picture 12 and your ready for the next 3 plugs on this side.

Step 19: Do the next 3 plugs in the same manner as steps 14 through 18.

You can either finish installing the other plugs but I like finishing one side completely so I don't have to come back to it.

Step 20: Reinstall fuel rail tighten to 89 in/lbs

Step 21: Reinstall fuel line by just pushing it back in with a firm grip and you will feel it snap back together.

Step 22: Make sure it you put the safety clip back on by pushing down on it.

Step 23: Reinstall the throttle body, tighten to 89 in/lbs. I think it is a lot easier to reinstall the throttle cable back on the throttle body before it is mounted. After the TB is reinstalled, put the cruise control and throttle return spring back on and plug in the throttle position sensor. Refer to picture 4.

Step 24: Reinstall you induction tubes and your PCV hose.

Step 25: Now with the passenger side plugs done and everything reinstalled you can move onto the driver's side. Notice there is hardly anything in your way. Do this side the same way you did the first. After you finish putting the fuel rail back on make sure you put the ground on the back bolt you took out. Refer to picture 18.

Step 26: You can now reattach you inertia plug in the trunk. Refer to picture 20

Step 27: Now reattach the negative battery cable. Refer to picture 21 and double check any vacuum hoses that may have come undone. Make sure you get all your tools out and accounted for. Start your car up and take it for a spin. Keep it under Mach 3!!!

Congratulations you have just changed your own spark plugs and learned a bit about your Pony.

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