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Where are the spark plugs and how do i replace them on an 03 marquis LS

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They are under the coils just above the valve covers. There are 8 coils, one for each plug. I suggest not using anti-seize on the threads, but you must use di-electric grease on the boots to prevent cross-fire. the Motorcraft plugs are good for 100,000 miles, and seem to work very well. be careful, there are not a lot of threads on the head (even fewer on 99-back) so don't over tighten them.

Posted on Sep 02, 2010


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1991 Grand Marquis LS Problem

Someone will need to figure out if you are loosing spark to the plugs or fuel pressure when it fails to start.

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My 1999 mercury grand marquis keeps throwing a plug. Mechanic says if it happens again I need to replace the whole head. Is this true?

You install spark plug inserts in the head

There are at least three of those tools avail

Lots to read about that problem on the internet

It went on from 97 thru 03,some 7 years,then ford
came out with a 3 valve 5.4 v8 that had two piece
spark plugs & they broke off for years.

The heads were designed with not enough thread
in the heads for the plugs & ford didn't care to resolve

You can read for days on just about any vehicle problem
on any vehicle going back 20 years

You don't or I wouldn't be pulling heads on a 14 year old car

Jan 28, 2013 | 1999 Mercury Grand Marquis

2 Answers

Where are the spark plugs located on a 2000 Mercury grand Marquis?

There are eight COPs (coil-on-plugs) to remove. Using a 7mm or 9/32" socket, remove each bolt securing each COP to the intake manifold on top of the engine. Remove all eight COPs, and the spark plugs are underneath. When replacing the spark plugs, use only the proper Ford/Motorcraft plugs, even if they cost twice as much as the aftermarket ones. You will avoid further headaches this way. Hope this helps.

Mar 30, 2010 | 2000 Mercury Grand Marquis

1 Answer

Jerking and hesitation between 35mph and 65mph

Time to go get it diagnosed. Could be a tunup issue or cranks sensor or fuel pump. You most likely have a code stored to help diagnosing

Nov 02, 2009 | 1997 Mercury Grand Marquis

2 Answers

Would like to know the gap for spark plug gaps for '92 Murcury/Grand Marquis LS..?

Think it is 0.54 but not positive. It should be listed in the back of your owners manual.

Apr 16, 2009 | 1987 Mercury Grand Marquis

1 Answer

Firing order 03 lincoln ls

starting from pasenger side first cylinder is 1,2,3,if v6 1,2,3,4 if v8
drivers side 4,5,6 if v6 and 5,6,7,8 if v8

Dec 23, 2008 | 2003 Lincoln LS

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