Replace the spark plugs: 1993 Mustang 5.0 (incl. Cobra)

How-to video

The video loads from YouTube (privacy-enhanced mode) only when you tap play. These videos are made by their channels, not by us. The LMR video gives a different torque range than the factory spec and pulls all the wires at once. This page uses the factory 7-15 ft lb and does one plug at a time.

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How we match videos: we only call a video from another year a match when a parts catalog lists the same part number for both years. If a video doesn't say its year, we say so.

Step by step

1. 1

   Let the engine cool and disconnect the battery.

   Work on a cool engine so you don't get burned. Disconnect the negative battery cable.

2. 2

   Clear the way.

   Move the air box or intake tube if it blocks the plugs. On the driver's side, the dipstick tube may need to move a little.

3. 3

   Pick one plug. Label its wire.

   Work on one plug at a time, start to finish. Tape-label the wire with its cylinder number.

   Do this before that: One at a time, so the wires can't get mixed up. If they do, the firing order is 1-3-7-2-6-5-4-8.

4. 4

   Take off the wire by its boot.

   Twist the boot back and forth until it is loose, then pull on the boot only. Never pull on the wire.

5. 5

   Clean around the plug.

   Blow or brush dirt away from the base of the plug.

   Do this before that: Clean before you loosen it, so dirt can't fall into the cylinder.

6. 6

   Remove the old plug.

   Loosen it with the plug socket and back it out. Look at it: black and sooty, oily, or white can point to other problems.

7. 7

   Check and set the gap on the new plug.

   Slide the gap gauge between the two electrodes. GT and LX 5.0: set it to 0.054 in (factory spec, source above). Cobra or a different plug: use the gap on your VECI label or in your factory service manual. Bend only the side (ground) electrode, gently. Never pry against the center electrode.

   Do this before that: Gap it before it goes in. Once the plug is in the head, you can't check or change the gap. Check every plug, even new ones.

8. 8

   Start the new plug by hand.

   Thread it in with your fingers (or the socket and extension, no ratchet) for several turns until it seats.

   Do this before that: Hand-start before the wrench, so it can't cross-thread.

9. 9

   Tighten to the factory torque.

   Use the torque wrench: 7-15 ft lb (factory spec, source above). Don't guess by feel.

   Do this before that: Gap first, then thread in, then torque. Never tighten a plug you haven't gapped.

10. 10

    Push the wire boot back on.

    Push it straight on until it seats firmly. Then move to the next plug and repeat steps 3 to 10.

11. 11

    Put everything back and reconnect the battery.

    Air box or intake tube back on, dipstick back in place. Make sure no wire touches the exhaust headers.

12. 12

    Start it and check.

    It should idle smoothly. Take a short test drive.

Mistakes to avoid

• Installing a plug without checking its gap first. Check and set the gap on every plug before it goes in, even new ones.
• Prying against the center electrode when you set the gap.
• Putting a GT/LX plug in a 1993 Cobra. The Cobra uses a different plug.
• Pulling on the wire instead of the boot.
• Removing all the wires at once and mixing up the order.
• Starting the plug with a ratchet and cross-threading it.
• Over-tightening. Use a torque wrench and the factory torque.

Done check

• Every plug was gapped before it went in.
• Every plug is torqued to the factory spec.
• Every boot is pushed fully on, and the wires are in the right order.
• No wire touches the exhaust headers.
• Idles smoothly. No misfire, and no check engine light.
• Pulls normally on a test drive.

Sources

Specs on this page come from factory service information, opened Oct 26, 2026. Where we could not find a sourced spec, we say so instead of guessing.

1. Factory service information, 1993 Mustang V8-302 5.0L HO: Spark Plug Gap (Operation CHARM)
2. Factory service information, 1993 Mustang V8-302 5.0L HO: Spark Plug Tightening Torque (Operation CHARM)
3. Factory service information, 1993 Mustang 5.0L HO: Firing Order (Operation CHARM)
4. Factory service information, 1993 Mustang 5.0L HO: Ignition Cable (spark plug wire) Service and Repair (Operation CHARM)
5. LMR: How To Change Mustang Spark Plugs (archived copy; tool tips, we did not use its torque)

Fitment sources: which years share the part

Motorcraft ASF42C is listed for the 1987-1995 Ford Mustang 5.0L V8 EFI, GT and LX. Fits 1987-1995 Mustang 5.0 EFI GT and LX with factory heads. The Motorcraft ASF42C listing says it will not fit the 1993-1995 Cobra.

1. LMR catalog (archived copy): Motorcraft ASF42C kit, fits 1987-1995 Mustang 5.0 EFI GT/LX, will not fit 1993-1995 Cobra or 1986

We only match years inside the same body: the Fox-body Mustang ran 1979-1993 (source).

Video model years

1. How To Change Mustang Spark Plugs - LMR Basics: LMR's published transcript: 'doing the work on this 1992 Fox coupe'
2. What You Need To Know About Spark Plugs For Your Foxbody Mustang or other 5.0 Ford.: No model year in the title or description