94-04 V6 Mustang Spark Plugs

Set of used spark plugs
Set of used spark plugs

Are you getting misfire codes? Engine running weak? Just have an afternoon to waste? These could all be good opportunities to replace your spark plugs. For all stock or bolt on Mustangs, it is recommended that you use Autolite or Motorcraft copper core spark plugs. These are what the car came with from the factory and have given the least problems over the years. Alternative brands include NGK, Zex, and Bosch however there have been a number of problems reported when using those plugs. They are, however, a good choice for a Mustang running forced induction (supercharger or tubro-charger) or nitrous oxide.

First let's start with the tools and supplies you'll need:

-Spark plugs

-Spark plug gap tool

-Spark plug socket (5/8")

-Ratchet (1/4" + 3/8") and assorted sockets + extensions

-Dielectric grease

-Anti-seize

-Torque wrench (that can read as low at 7 ft/lbs)


The first thing you're going to want to do is unhook your negative battery connector. I find any time you need to unplug sensors, it's safer to unhook the battery. With that unhooked you can begin removing your air intake tube. There are 2 latches to flip up on the air filter housing then 1 bolt holding the housing to the fender. If you follow the tubing a very short distance you'll find an electrical connector. Unplug this and continue following the tubing until you find a hose that leads to the crankcase. Remove this hose from the tubing but because as it may have started to dry-rot. Finally use your ratchet and appropriate socket to loose the hose clamp. At this time you can remove the entire air intake tube and set it aside (be gentle, the mass air sensor inside is delicate).

If you haven't already, use your spark plug gap tool to gap all 6 spark plugs to .054". I found a pair of sturdy needle nose pliers worked well for getting the gaps just right.

With all preparation now made, it's time to move on to the park plugs. I recommend starting on the passenger side as it is more difficult (save the easy for last). Follow the spark plug wires until you find the boot (the part that connects to the spark plug). Pull one off for now (this may required a little twisting as the boots can get stuck on there tight) or else you risk putting them back on in the wrong order.

Using your ratchet, an extension, and your 5/8" spark plug socket, remove the first spark plug. Take a look at the spark plug and determine if there are any visible problems. If there are then you should look further into the problem. If not, continue on.

Grab a new spark plug and apply a tab of anti-seize to your finger then brush it around the threads on the spark plug. This will make the spark plug easier to remove when you need to change them again.

Using your extension and spark plug socket, put the spark plug into the socket and line it up with the hole that the old one came out of. Tighten it down by hand then grab your torque wrench. Set your torque wrench to somewhere between 7 and 14 ft/lbs then finish tightening down the spark plug.

Get your dielectric great and put a dab into the spark plug wire boot. This will ensure a good connection as well as make the boot easier to remove in future spark plug changes. Put the boot onto the new spark plug. The boot may make a small "pop" feeling, letting you know it is securely in place. If that boot has been previously damaged it may not "pop" into place, but may still make a good connection.

There you have it, one down and 5 to go. Repeat the process for each of the 5 remaining spark plugs. You may have difficulty remove the 2 spark plugs closest to the firewall, but keep at at it because they will come out.

When you have all 6 spark plugs replaced and the spark plug wire boots securely reconnected you'll need to reinstall your air intake. Start with the tubing. Using the hose clamp, secure the tubing to the throttle body and reattach the hose from the crankcase as well as the electrical connector to the mass air sensor. You may want to take this opportunity to apply a small amount of dielectric grease to the electrical connector.

Now put the air filter and its housing back into place. Clamp it down to the tubing using the clamps connected to it and bolt the housing back to the fender. Reconnect your battery then start the car up. Watch for any check engine lights or odd sounds/sounds from the engine. If everything runs well go ahead and shut it down. Go clean yourself up and be proud of a good days work!

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Comments 4 comments

graypony4@hotmail.com 5 years ago

No No No autolite is GM


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Cobrafan 5 years ago from Nowhere Author

Autolites work very well on Mustangs. I know a lot of guys who swear by them.


tj 5 years ago

can i use motorcraft platinum or use autolite copper?


Cobrafan profile image

Cobrafan 5 years ago from Nowhere Author

Motorcraft or Autolite coppers are recommended

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