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Spark Plugs - Changing With UIM In Place

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Changing Spark Plugs With UIM In Place


I've noticed this keeps coming up in the V6 section so i've decided to write a HowTo on it with pictures to follow. If you use the right tools it's a simple task which should take 15 mins max.


  • Decent 10mm spark plug socket with inbuilt rubber plug gripper.
  • Three 3/8 extension bars, one of which should be a 'wobble' type
  • Feeler gauge set.
  • 3/8 Universal joint to fit extension bars.
  • Rachet handle.


  • Set your replacement spark plugs to 1.3mm with the feeler gauge. (NGK plugs are all preset at factory)
  • I recommend starting with the front bank of three plugs. Access is easier and experience gained will help when replacing the rear bank of plugs, which are far less accesible.


  • Remove the front plastic cover then the four 8mm screws securing the IMRC. Move the latter aside, as necessary to clear the plugs.
  • Choosing the most accesible plug lead, squeeze the associated rubber seal sideways to release it from the head, then firmly pull the lead and attached plastic tube upwards, to release the connector from the plug. Withdraw the lead assembly from the plug location hole then lay it aside.

When removing plugs from the front bank, the bulkhead does not limit access therefore, all three extensions can be connected then taped together and the plugs removed as follows:

  • Attach your plug socket to the plain extensions, then tape into position with 'gaffer' tape or similar.
  • Carefully lower the socket and attached extensions down the hole. When the socket engages the plug, ensure it locates squarely then, using finger pressure only, push until it locates fully on the plug. Connect the ratchet handle, via the universal joint if necessary, then unscrew the plug until it is free from its location. Remove the ratchet then carefully lift the extensions assembly until the plug has been safely removed.
  • Apply a very small amount of anti-seize compound to the plug threads then fit the replacement plug securely into the socket. Gently lower this assembly down the hole until the plug threads engage squarely. Gently rotate the extension assembly counterclockwise, to prevent cross threading, then screw clockwise, by hand, until the plug is correctly engaged with its thread. Tighten by hand until fully engaged, then fit the ratchet and tighten gently. Correct torque is only 15Nm (11 lb-ft) which is approximately a quarter turn from hand tight. CAUTION: Do not overtighten.
  • Repeat the same procedure on the two remaing front bank spark plugs.
  • Refit the IMRC unit and the plastic manifold cover.
  • Start the engine and check it is operating correctly.


  • It is very tight at the rear and space can be made by first removing the coil pack power lead, then removing the plug leads from the coil pack, after noting their correct positions. If necessary, remove the coil pack, noting the position of the earth bonding leads. Genuine Ford leads and coil packs have the connections clearly marked.
  • All of the rear bank plugs have limited access and the bulkhead overhang prevents the necessary length of extension to be inserted into the plug hole in one piece. Therefore, the three short extension bars must be carefully added in sequence as allowed by the bulkhead.

Note MK1: Having just changed my plugs on my MK1, I had no need for complex extensions. A single normal ~25cm 3/8" extension passes into the rear plug chambers without problems. Just remove the coil power and HT Leads. By TwinTurbo

  • Starting with the rear inboard plug, which is the most accesible, remove the plug lead from the plug, as described for the front bank.
  • Connect the first extension to the plug socket, then secure with suitable tape to prevent it coming apart.
  • Carefully lower the socket and attached first extension partially down the hole, until a second extension can be added without fouling the bulkhead. Lower this assembly until the third wobble extension can be added. When the socket meets the plug, ensure it locates squarely then, using finger pressure only, push until it locates fully on the plug. Connect the ratchet handle, via the universal joint if necessary, then unscrew the plug until it is free from its location.
  • Continuing in the same manner as that detailed for the front bank.
  • When refitting the new plugs, each extension piece must be added consecutively, as previously described for removing.
  • Reconnect HT and coil pack leads. Secure coil pack, if removed, then double check everything's back in place and secure
  • Start her up and make sure there are no misfires or sluggishness

Disclaimer: I'm not responsible for any errors in this guide or errors you make while following this guide. Any doubt don't be afraid to take it to your local garage