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Engine stutters sometimes:

Have a 2002 Mercury Grand Marquis LS, with

103000 miles on it. Replaced radiator hoses

flushed engine, and replaced antifreeze. At

the same time replaced spark plugs with AP104

plugs from as Napa auto supply. Upon conclusion when running at 60 mph, engine

stuttered, then check engine light showed

up. Test showed cyclinder 1 misfiring, reseated plug wire, runs better, for awhile. Now it begins again with the

engine stuttering, but light does not

come on, and it is not as bad as it was

at start. Any suggestions as to problem?

I assume you had no problem before the above work.
Did you check the gap on all plugs? If so…

Could be a bad plug.
Could be a bad coil.
Did you damage the wiring to the #1 coil?
Is there coolant in the plug well?
Is the plug correctly screwed in?

A mechanic friend did the work saving me 400.00 from estimate given by a Goodyear
place. Have not called him after he fixed it first time, wanted more detailed
information to ask questions better. He said access to plug wire on cyclinder 1
was very difficult and felt he may not have seated it properly, which fixed it
for about 2 weeks, but it appears to be restarting to stutter again but not as
harsh as first time. I believe plug has been installed correctly, and gapped. Was
wondering if there plugs were the correct type. My friend hinted we may need to
replace them with Motorcraft, if the Autolite ones continue to act up. Does this
sound possible?

Autolite should be okay. I am confused by your mention twice of “plug wire.” This car does not have any plug wires, it is Coil-On-Plug. I don’t recall ever having any trouble getting to any of the plugs on this car.

I’m not sure, he may have used that terminology to make it easier for me to understand.
Last time I worked on a car, ignition, engine and etc, was back in 1970, and then it
was on older vehicles then that, like 1950-1968. I would need to talk with him before
I can say much more, so will check with him and then respond again in a day or so.
Thanks for your help to this point. Will let you know what happens.