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Why would only the rear cylinder spark plugs be corroded after they were just replaced 1000 miles ago? All of the other plugs are beautiful.
The corrosion looks to be a light brown/tan color. Is that antifreez? Is this a common problem for these motors?

Like I said it is only the rear 2 cylinders....dont know the numbers off the top.
But they are the furthest back on each side.

The car has a slight miss also.

This is a 1990 towncar BTW...5.0 non H/O

Thanks
 

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this is pretty normal since the rear cylinders are farther away from the water pump and therefore run hotter. the brown/tan color is normal, especially if your driving style is somewhat on the... spirtited side :) . all my plugs are that color, they still work fine, its just from the heat. the miss may be from elsewhere in the ignition system, check the cap, rotor and wires.
 

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What a great explanation.."spirited side". Will have to remember that.
 

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Yup... spirited driving coppa...

Those plugs would be the #4 (passenger side) and #8 (driver side). That's somewhat normal, those two can be a little starved for air due to the intake design. The tan color is actually really good, if it's white or black, then there'd be a problem. The tan color is actually what you want.
 
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