2 months ago I bought a used 99 mustang 3.8L V6 with only 72K miles...
I recently gave the car a tune-up and found out the following:
Old spark plug gapping: @ .072
New spark plug gapping: @ .054
Under the hood there is a label which states that the range should
be between .052 - .056
I bought bosch platinum spark plugs and the gapping was: @ .062
what should I go by? How much does this affect the engine? Would
this keep the engine from not idling properly?
> 2 months ago I bought a used 99 mustang 3.8L V6 with only 72K miles...
>
[quoted text clipped - 10 lines]
> what should I go by? How much does this affect the engine? Would
> this keep the engine from not idling properly?
I'll let others answer the technical aspects but I'm curious why you
wouldn't follow Ford's spec. I wouldn't think the gap set at the Bosch plant
has any relevence to a specific application.
Richard
> 2 months ago I bought a used 99 mustang 3.8L V6 with only 72K miles...
>
[quoted text clipped - 10 lines]
> what should I go by? How much does this affect the engine? Would
> this keep the engine from not idling properly?
A larger spark gap requires more energy to make a good spark. Too big of a gap
will decrease efficiency, decrease fuel mileage, and increase emissions.
Just set it to factory specs and don't worry about it.

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> 2 months ago I bought a used 99 mustang 3.8L V6 with only 72K miles...
>
[quoted text clipped - 10 lines]
> what should I go by? How much does this affect the engine? Would
> this keep the engine from not idling properly?
I'm curious why you would buy Bosch..
If you paid attention on here and alt.autos.ford, you would know that
Bosch Plats didnt run good in ford distributor cars. Single plat
application, obviously.
For ME that is enough to rule them out, FOREVER - even in DIS cars, as
people never seem to have trouble with the designated Motorcraft plugs,
anyway.
The classic symptom of Bosch Plat in Ford is random miss at idle speed
and at cruise. Watch for it.

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walt peifer - 18 May 2006 17:07 GMT
>> 2 months ago I bought a used 99 mustang 3.8L V6 with only 72K miles...
>>
[quoted text clipped - 23 lines]
> The classic symptom of Bosch Plat in Ford is random miss at idle speed
> and at cruise. Watch for it.
I agree go with the motorcraft double platinum plugs. plat tip and
electrode. set at factory specs and you may want to change plug wires while
your at it. the silicon wire will look good forever but do start to
breakdown internally at around 100k to 110 k miles
Schadenfreudist - 20 May 2006 07:36 GMT
> I'm curious why you would buy Bosch..
> If you paid attention on here and alt. autos.ford, you would know that
> Bosch Plats didnt run good in ford distributor cars. Single plat
> application, obviously.
> For ME that is enough to rule them out, FOREVER - even in DIS cars, as
> people never seem to have trouble with the designated Motorcraft plugs,
> anyway.
> The classic symptom of Bosch Plat in Ford is random miss at idle speed
> and at cruise. Watch for it.
Ummm. I'm fairly new to this group and use bosch plat singles in my '75 II.
What is this about them being bad? (hate re-stir things up)
Schadenfreudist <hehe@hehe.hehe> Fri, 19 May 2006 20:06:23 -0700
Backyard Mechanic - 20 May 2006 11:51 GMT
> > The classic symptom of Bosch Plat in Ford is random miss at idle
> > speed and at cruise. Watch for it.
>
> Ummm. I'm fairly new to this group and use bosch plat singles in my
> '75 II. What is this about them being bad? (hate re-stir things up)
Sorry... should have qualified that to TFI equipped... I have no idea on
Duraspark or points cars.
SEE above... appears in a couple thousand miles.
But, AGAIN, Motorcraft makes great plugs.

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Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!