When is it time for new plugs and wires?

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My 04 Ford Ranger manual suggests changing spark plugs and wires 10 years/100k. I can't wait that long,considering I have less then 37k after 5 years. So at what mileage/or time is a better time to change out the plugs and wires?
 
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Pull the plugs for examination and put them back in. Will help keep them from seizing. A dab of dielectric grease on the plug boots will help them come off next time too. Let well enough alone, factory ignition stuff is high quality.
 
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I changed my plugs in the Tacoma after 69500 miles. The electrodes were clearly worn down at that mileage. You would have never known it since it still ran perfect before the plug change. I would change plugs at 70000 and leave the wires alone.
 
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The plugs may be great for a long time if they are precious metal tipped. But wires are exposed to air/heat/etc. and can break down even with not so high miles. In your case, I'll bet they are both in great shape. Ford uses platinum tips, and they have always made the best factory wires.
 
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OEM's wires are very high quality, '94 LS400 with more than 240k miles and '00 MB E430 with more than 105k miles still have OEM wires. '94 LS400 is on third set of plugs and '00 E430 is on second set of plugs.
 
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 Originally Posted By: Superbuick96
My 04 Ford Ranger manual suggests changing spark plugs and wires 10 years/100k. I can't wait that long,considering I have less then 37k after 5 years. So at what mileage/or time is a better time to change out the plugs and wires?
My Taurus had the same recommendation and the plugs/wires were toast around 70k miles and 5 years. Threw a CEL and started running like a misfiring helicopter. Had to get them changed out.
 
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I'm on my 1st replacement wires on my 96 Sunfire. First OEM wires went to 93k miles, I went ahead and changed them since I was doing the factory OEM plugs at the same time. I've had no problems. My 2nd set has 72k/8 yrs on them so far
 
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Sep 11, 2004
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Every car is different. I have had early 90s FoMoCo vehicles with the 4.6 eat plug wires in 15K miles (which is why the wires went through 4-5 upgrades over the years). I recently replaced the original plug wires on my '73 J4000 when I replaced plugs on it. The wires were the original numbered factory wires and close to 35 years old. Still worked OK, I was just paranoid. OEM Ford platinum plugs can easily go 100K miles. I have pulled out factory plugs (originals with the paint dabs on the tip) from 100K+ mile vehicles just because the customer was following the maintenance guide. They could have gone longer. Couldn't guarantee they would leave all of the threads in the head though. If it ain't broke, don't fix it. You will know when you need to replace wires. 10/100 is a valid maintenance interval for plugs/wires.
 
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My dad had a friend with a 97 ranger with the twin spark 4 cylinder. It started missing when it hit 120k, in 08. He kept putting it off because 3 of the 8 were under the intake manifold. I don't know of he ever did it.
 
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Punisher, how long is the max time that plugs should be left in a head? Mine have been in for 6 years (65,000 miles) and when I took one out it to check them it almost felt like the threads were being stripped.
 
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